If you ask me, that totally makes sense too. Also, I see it this way:
Let's say I only log in a play games, never make them, and never rate them. I would have to manage to log in every day in a year to get 365 xp. And, since rating doesn't require comments to get the point (if I understand it correctly), one can be shy and silent and still get the points.
Now, If someone actually is interested in writing and rating, they're more likely to log in and remember these things. Plus, they're getting the points from what they actually do on the site.
But, the daily point existing, and not being automated, means that if people DO care about the XP, for whatever reason, it means they're logging in. Every day they log in, the chance of them getting inspired to write a game, post on a forum, or rate/comment a game is higher than the days they don't log in, obviously. One day something might catch their eye as they're looking to get that one little point.