Pretty much what you and Lhutz say, even AAA buy assets and textures. For the most part they don’t go around scanning PBR images off bricks and the like, also having base meshes for indies saves soooo much time. It’s pretty much the only way smaller teams can tackle larger games, then you just modify them to suit your needs and nobody really cares about mundane things like rocks as said. Plus buy enough and there’s potentially thousands of combinations that I doubt anyone else will use.
Sure, you do need to put in additional effort to make games look unique whilst using bought assets. But still it’s better than starting from scratch… Also frameworks and materials etc. just speed the whole thing up.