games directory?

It's just a bit of historical cruft. A long time ago, games were an optional part of the system, and might be installed by different people, so they lived in /usr/games rather than /usr/bin. Data such as high scores came to live in /var/games. As time went by, people variously put variable game data in /var/lib/games/NAME or /var/games/NAME and static game data in /usr/lib/NAME or /usr/games/lib/NAME or /usr/games/NAME or /usr/lib/games/NAME (and the same with share instead of lib for architecture-independent data). Nowadays, there isn't any compelling reason to keep games separate, it's just a matter of tradition.

At least partially, it's so the system can have a games group that certain users are members of, and they all have rights to execute games in the games folder