What kind of RCS is used always depends on the organisation. We are actually using GIT and SVN, and both make sense for the departments that are using them.
While I'm not using it, since we started our small-team hobby project in git and moving away from it would be a bother, there is one use-case of SVN that would save us a lot of headaches.
SVN being centralized means you can lock files. Merging Unity scenes together is really pain, the tooling mostly doesn't work properly and you have no way how to quickly check that nothing was lost. Usually, with several people working on a scene, it resulted in us having to decide whose work we will scratch and he will do it again, because merging it wouldn't work properly and you end up in a situation where two people each did hundreds or thousands of changes to a scene, you know that the Unity mergetool is wonky at best, and checking that all of those changes merged properly would take longer and be more error prone than simply copying one persons work over the other.
We resorted to simply asking in chat if anyone has any uncommited work, but with SVN (or any other centralized VSC, I suppose) we wouldn't have to bother with that - you simply lock the scene file and be safe.