Don't their artists and designers use version control too? Maybe they just have one such person per team, or each person owns one file, or something like that. Hard to say.
Maybe it's like how I used to work on teams that never used branches - you have various problems that you figure there's probably a solution for, but there's never time to (a) figure out what the solution looks like, (b) shift the whole team over to a brand new workflow and set of tools, and (c) clean up the inevitable mess. So you just work around the problems the same way you always have - because at least that's a known quantity.