Wrong, Apple does not provide any additional features besides taking a cut. Sure, maybe they provide the payment process, but that's it. The moment you subscribe, you might as well forget Apple exists.
Steam, on the other hand, allows: cloud saves, family sharing, media library, big picture, controller support, Linux support, achievements, community, friends, groups, store with tag search, advanced review features, inventory, couch coop over internet, and fuckton of stuff.
I'd say 30% is pretty generous, given Steam's reach. Also you are not forced to use Steam, you can you GOG, Epic (eww), Ubisoft, EA, Amazon, etc., while with Apple you can't.
You'd be surprised how many people don't brush their teeth, let alone twice a day, and let alone floss. Those who do the correct shit will probably not feel the difference, those who don't will lose the only protection they had left.