If you think that every corporation is an Evil Corp and actions are evil because evil entities do them then there's no reason you should care.
But if you ascribe the degree of evilness to the action rather than the actor, then you absolutely should care because it's anti-competitive and poisons the general health of the market.
true. in general I would agree any party taking a 30% cut (whether app store or play store or whatever) would be the supreme evil. but since all three parties involved in this instance are of the same caliber, I don't care, and I choose to use none of them.
It's a fair choice to use none of them, but the problem with large entities making decisions you don't like is that the next step from "large" is "institution" (which Apple arguably already is) and then sometimes "dominant institution."
So if you buy the slippery slope argument (which you don't have to), then if there are objections you want to make about that dominant-institution-in-progress, now is probably a good time to think about what they're doing and what you wish would change.
But if you ascribe the degree of evilness to the action rather than the actor, then you absolutely should care because it's anti-competitive and poisons the general health of the market.