Beslan covered this very nicely, but for a bit of background, I added this rule because it's shocking how many games get submitted without any sort of author credit.
If there's a download version of your game and I decide to boot it up any time in the future, I won't have the game page to tell me who made it. So it's important that the game tells me, whether it's your actual name or a handle. Then if I enjoy it, I can look you up and find more recent projects or other things you're working on.
On the more sinister side, it's almost impossible to prevent others from hosting your game on another website without credit. If you put your name in the game, it's much more difficult to remove that credit.