Because I feel better about mailing out email notifications for new batches of games there, I don't think people would appreciate it on here as games are only *optional* parts of the Arcade.
Unlicensed members can download those games, but the games aren't hacks themselves - and they don't do much without the Arcade, which can only be downloaded by licensed users.
And thirdly (and probably most obviously), it's to get people to sign up on the Arcade site - mainly because I'm going to need a lot of people to test the next release, which works best on a site where people are actually visiting.