The world isn't randomly generated for a bunch of reasons, don't know all of them but one of them was that to actually make that program to randomly generate a world like this is also a lot of work and we'd still have to go in and fix things by hand and have to check everything so it saves some work but it really depends on what the intention of the game is and what

your level design team is like and such and the choice at the time was handmade and we stuck to it.