Marfitalu: On the Go fellowship there was a discussion on that issue. (You are welcome to join.) The reason they are unrated is because that is the easiest way now. Maybe Fencer will change some things later, I do not know. I myself see the game as in a kind of testing stage, probably Fencer is glad to hear about unexpected problems and possible points of improvement (like the 'correct' komi etc.).
Go is much harder to implement than most other games although the rules are simple.