This is intentional; game binaries install themselves as setgid games when they need to maintain high score files that can be edited by the games themselves but not by ordinary users. Adding users to the games group would open a security hole, albeit a minor one. Any game that requires the user to be a member of the games group is misconfigured.
-- User does not belong to games group https://launchpad.net/bugs/80347 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
