I think we have a God Card mix-up here. gabrele is talking about the Wicked Gods (Eraser, Avatar, and Dreadroot), which are allowed to be played. Digital is probably thinking of the Egyptian Gods.
For one thing, the Wicked Gods require 3 Tributes to be summoned so you have to put a little work into getting one out. They can't be Special Summoned, so making sure they survive is important. Their effects are useful in some situations but they aren't necessarily groundbreaking. Since there are also plenty of monster removal effects that are used, not being able to destroy them in battle, if that's the case, doesn't pose too much of a problem.
Basically, you need to put a bit of effort into playing the Wicked Gods, so any sort of limitation for them isn't really needed. That's why you don't see them used in high level tournaments, if at all.