Steam was established earlier than the App Store, and everything you buy there is very locked down to the Steam platform. Try uninstalling Steam and still play your bought games and they wont work.
Also Steam has an even higher rate than 30%. Yet Steam get a free pass in most rants like this, why is that?
They also don't have a history of making inconsistent review decisions that seem to be business oriented rather than customer oriented. I'm sure there's some examples, but most of the publicized removals have been for things like totally broken in unfun ways games, and games where a totally different game was published in the same slot. Often, customers get refunded for purchases when things like that happen.
I think Steam has also earned a fair amount of goodwill by not being as terrible as most other game download services, but maybe that's just my perspective.
This page is just a quick Google away: https://steam.fandom.com/wiki/List_of_DRM-free_games