Not sure where this is coming from. Most AAA studios have been using Perforce for decades. There is a smaller contingent using Git, mostly mobile and indie games. UE is not different in that respect. We have to deal with large, versioned binary assets in game development, something that Git struggles with (without things like LFS that are hacking around the architectural problem).

I don't know what to say about a studio not using source control in 2021. I see student projects regularly with full version control and CI.