They have special rooms with a capable machine set up, and you check in. Or, apparently for some, you can check OUT a game console to play the game at home.
Additionally, I can run Portal satisfactorily on my $250 computer. Not that this makes it accessible to every single person- some people cannot afford $250- but the number of people unable to play will be drastically reduced in the very near future.
Should money be associated with these things? If you feel the answer is 'no', remember that books cost money to buy, and so do movies. It is a bit harder to rent a video game and PC at the library, but we're getting there.
(It is important to remember that while culture may be free, the medium is not. It is also important to remember that 'Library' just means 'Someone else is paying', albeit at a reduced cost.)