Any source for this? The way the engine works, you can't just start working on a gameworld and then mid-dev decide to scale it down. You'd have to rebuild the whole world for that.
IRRC ~somewhere in Todd's speech at George Mason University, he recounts [
paraphrasing here] of how they had created a vast expanse of landscapes, but that during playtesting, they found that it just wasn't fun [in FPP?], so he cut it; and made some [harmless] jokes about having to tell the designer that he was erasing the last several months of their work.
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Fallout's setting is in abject desolation & ruin, with survivor perseverance, but not a lot of hope; this...seasoned with black humor to offset the excruciating oppressiveness. FO3 [mistakenly] tries to put the player personally into the world; one where I would say that they were never welcome, nor invited... nor should want to be.
The Fallouts' depicted a person born in that mess, poked (by great need) into embarking upon someone else's agenda ~their family's agenda..."Get this thing or we'll all die here!". We get to see that play out.
FO3 & 4 put the player in the world ~personally, and what pokes them into action is imminent death if they do nothing. In FO3 it comes at the hands of their backstabbing community. In FO3 & FO4 when they escape the vault, they don't really have much reason to go back. They are instead expected to enjoy the filth and despair of the outside world. We don't get to see that play out like in Fallout or Fallout 2. In the Bethesda games we're stuck in it, and forced to wallow through it like ants in a city dump.
It's really interesting to me that for a detached game like Fallout, a big map is an incentive to explore; but in a 1:1 [or even 1:16] first person game, a big map is a chore; filled with busywork encounters. If playing both games, and having three fights while traveling from point A to B, in Fallout that's three back to back challenges; in FO3 & 4 that's three spaced apart intermissions during a long hike through trash.
The wasteland is an intentional hardship in Fallout, it's what you have to walk through [for days or weeks], to get to where you need to be; but in FO3 & 4 they want it to be a themed attraction, a shown off incentive... come experience the trash! Vehicles would make the trash heap [world] something seen only passing in the window, and not thought of again. Vehicles would also be a pain in the ass to handle debris in cramped and open areas alike. Presumably there could even be glitches that could send the driving player high into the clouds ~like those bugged deathclaws.
Also [and perhaps the biggest hurdle] is the NPC combat AI's treatment of a PC using a vehicle.
Here is a mod I did many years ago:
