Im not really complaining about them but why are they allowed? what is it about them that makes them okay? the fact that the infinite can only start due to you making a mistake?
They are allowed. The reasoning behind allowing infinites is that
one, you can’t really forbid infinites without getting into a mess of other sticky stuff - what about this combo that is almost as good as an infinite (or better, even) but isn’t one? What if I do an infinite but I don’t complete it to 100%? What if I only use two loops of the infinite? What about 100% combos that aren’t infinites, are those just as bad?
And two, if you get caught in an infinite, yes, it’s usually your fault.
However, some infinites are indeed really cheesy (see: Dong Dong Never Die, a game with a character who can infinite you at any distance if you do anything except block)… and if that’s the case, the game usually never makes it to competitive status in the first place. Or the offending character itself might be banned, as with HDR/ST Akuma.
It’s hard to explain to someone who doesn’t play a game that they exist in. Just because an infinite or 100% combo exists, it might have a contrived setup, or be in a team game which mitigates the seriousness of losing a character to 1 combo, thus not really breaking the game at all.
If there are enough practical infinites that have loads of setups in a game, people just won’t play it.