Of course, I'm giving you my perspective on it, and mention people who played differently. But I'm going to talk about what I know.
Recently, I realised there's something about me and the people I play with that I don't see as much on Western RPG forums. Namely, some people seem to need adventures in order to run a game.
I don't even read them most of the time. Why? I simply don't use adventures, pretty much never*. The books the help me running a game would be setting material, especially if it presents some faction's or religion's outlook on some major conflict in the setting (something like Caste Books/Masters of Jade for Exalted...which are setting books, if you're unfamiliar with Exalted lore. Or the Sunward in Eclipse Phase. Or Behind the Eyes of Madness for my current FWTD game).
I'm double more likely to use some setting material if it leads to social upheaval, BTW. Like "here are those inventor guys we mentioned in passing before. Yeah, they've perfected water mills, and now use them for forging stuff as well... so they can mass-produce armour if they get the raw materials".
(That would be boring and like-a-handbook to some people. I can center a campaign around such a detail. I guess "boring" is relative).
But - back to the topic - I'm simply not used to using adventures. I'm used to passing without them, to the point that it literally takes me longer to read and prepare an adventure, than to construct one myself. I mean, I'm using about 15 minutes per session, for major campaigns, usually in the bus while travelling to the place we've decided to gather that week. I need longer than that to even read a 32-pages module, and even longer to extract the information I'd see as "useful".
Yet some of my players wanted to write a novel, a series, or a short story****, about my campaigns. I guess it's not impeding my ability to have fun stories emerge in gameplay.
See why I like the "Lazy GMing" moniker and proudly display it on The Big Purple?
So, in short: we couldn't get adventures when I was learning to GM. Hence, we learned to make our own early. It's still largely expected the GM would be running their own campaign, too - I think I've seen less than half a dozen people asking about which adventure to run next.
Actually, the last one said "now that we finished (a customised Keep of the Borderlands, I think), I've got time to cook my own campaign. But just in case I'm not ready, what would you recommend me to run in the meantime?"
The answer was "X isn't all that bad until you settle on something more long-term". Long-term games are definitely expected to be "GM-prepared". Again, it depends on the group - but that's an almost unquestioned consensus on the Bulgarian RPG forums. Yes, it's not in any way unique about me and my groups.
*I've tried GMing some modules for the regulars, just to see how it works. They effortlessly broke the railroad/plot-based one - I just rolled with it, but it means I could only use the opening scene. Next time I tried it, they almost effortlessly ended the events-based one prematurely, without really trying. Keep in mind, their actions were entirely logical, or I wouldn't have rolled with it - I actually wanted to run a module. Just to see what it's like, if you can imagine what it is to have run games for around a decade without ever using anyone else's adventure.
Still, the only one that worked has been a mission-and-events based one adventure from the FWTD, and that was as a part of a larger game where most PCs didn't even know about said "mission".
I'm now wondering what they would make of a site-based adventure. I suspect they would make of it...fun. Last time I showed them some OSR material detailing a whole city, the comment was "Did you say OSR or OCD? Seems like OCD to me to detail all of these NPCs in advance" (and she's studying for a psychologist, so it was doubly more funny. Of course, it was obvious she didn't mean it).
BTW, that's not in any way unique for the Bulgarian GMs, especially those of the "first and second generation" like me. Most of us simply had to make do without anyone's help and without additional published materials... often for purely financial reasons**. So we've had to gravitate towards GMing styles that only use setting info and what the player's backstories contain. I remember a thread from a Bulgarian RPG forum - the biggest one - where one of the "more fortunate" GMs (meaning one who had the means to acquire adventures and was used to running them) posting a poll. "Do you prefer site-based or events-based adventures?"
The answer was a pretty overwhelming "Fuck that, character-based for me!"
Keep in mind, I'm not complaining! Just explaining why I have almost no use for something most GMs in the USA and UK use widely. Personally, I find my GMing style only got better by the lack of pre-packaged materials. Because it's always custom-tailored for the campaign, and according to my players, this shows. And I'm now in the habit of not using adventures.
Consider this: first-and-second wave GMs in Bulgaria have been running games since about 2000-2001. That's nothing compared to some people on RPG.net, but the fact is... it's enough to learn a certain style of GMing, or more than one in my case (I've fluctuated a lot). Since we've never had to use adventures, and most of us couldn't even if they wanted, until recently, it means we've already learned some styles of GMing where the adventure is simply something that doesn't exist.
And we're the ones teaching the new GMs. So, unless they're self-taught (since today, they could possibly afford an adventure AND a rulebook), they would be running it like us.
Funny enough, when Vincent Baker, the author of Eberron, came to Bulgaria (he wrote about it in the Escapist), he had met some of those guys that had the money/connections to get adventures back then. They're also a much less of a DIY crowd, as their whining about lacking polyhedron dice*** showed.
**In Bulgaria, most of those the first-and-second wave of GMs had started GMing at the end of the 90ies or the beginning of the 2000s. An adventure from Amazon could easily reach 50% of a monthly wage for what people in the beginning of the 2000s were making, or - hold to something - more than a montly salary in some years of the 90ies. Well, I wasn't playing in most of the 90ies, but you get the idea.
A new adventure every month? As you can imagine, that wasn't possible for most of us, period. So, we litterally couldn't afford having adventures.
***Several other groups just emulated the spread of probabilities in polyhedron dice with d6. And I mean with equal probability for every number.
For example, a d12 isn't rolled by just rolling a 2d6. It's rolled with two clearly distinctive d6, one of which is to be the "number" die, and the other, the "heads or tails" die, because it's acting as a d2. You use distinctive dice (my favourites being a black and a read one) in order to be able to to throw them together, but to read them separately. All the methods of emulation were based around it.
So, take the number the "nimber" die is showing. Heads, leave it as is. Tails, add 6 to it. You've got a d12 now! (Alternative method: multiply the number on the "number die" by 2. Head, leave it as is, tails, subtract 1. That was actually what I was using, since multiplication is as fast as addition to most of us). And you can do the math, if you don't believe me - it's got exactly a 1 in 12 odds to roll any particular number!
Admittedly, rolling a d100 was more complicated, and usually required rolling 2d10 in order, not together. But it worked, too.
The only reason we even bothered to get polyhedron dice were the dicepool systems. Some got them for WoD, I personally wanted to play TRoS, and others wanted to play Exalted. I already had got a standard set of 7 dice just for the d100 rolls, which I needed for d100 systems.
****Curiously, all of them cited different things they had liked - but then, these were different campaigns.
One of them thought it's been an epic story (it was a mythological steampunk with strong ecological elements).
Another wanted to make a short story from another campaign, because they thought it "feels like life and not fiction". Yeah, that's exactly what I was going for, indeed.
Yet another felt another campaign has been like soap opera...except with sex and violence.
In all 3 cases, that was the feeling I have been going for. I'm proud with all 3 offers (as you can tell). Sure, I'll believe any of them might carry through with it when I see the first draft. But the offers sure were nice!