It's to make the site more "prestigious."
I think it works for them.
It really does TBH.
It also puts more fear into users. If you get banned, have fun waiting for a couple months to make another account =P. It's not like anybody can sign up and 10 minutes later they start trolling or w.e
Plus there's quite a few game developers on the site. I know Rushy is there and he is the director of DriveClub.