I think coming up with one set explanation for why all martial powers are limited isn't going to work well. There's always going to be a few powers that defy any mold you create. And developer time can probably be better spent than coming up a detailed explanation of the natural limits of every martial power they create.
Personally, I tend to explain stuff like this on a case by case basis. It might be that no-one ever falls for Explosive Badger Trouser Suprise more than once per fight, while Super Hippo Slam is just too exhausting to use more than once without taking a breather first, and Crimson Edge requires incredibly precise timing and luck for even the most skilled fighter.
Personally, I tend to explain stuff like this on a case by case basis. It might be that no-one ever falls for Explosive Badger Trouser Suprise more than once per fight, while Super Hippo Slam is just too exhausting to use more than once without taking a breather first, and Crimson Edge requires incredibly precise timing and luck for even the most skilled fighter.