No, of course it’s not surprising that they’re not a charity. Sure, the big app stores exploit their near-monopolies with exorbitant fees.
Good for Apple, Valve and Google, but I think it’s better that game dev studios and app developers get money instead. However, devs don’t currently have a real choice but to pay up.
Competition can change that, so we should support technically worse stores like Epic so developers will not have to pay their unreasonably high fees.