data siphoning, advertising, forced account nonsense to pad numbers and skirt steams cut in money.

they are useless to users and mostly have zero reason to run the game(s).

but, you can bypass a lot of them, most notably, the ones that are separate from the game.

examples of the above being paradox, 2k/fraxis and others (also to note, 2k/fraxis retired their launcher, so we dont have to bypass it anymore).

but, ones built-in to games, are a bit trickier, need more fiddling.

as for games that use them and have anitcheat, usually cant be bypassed and may have consequences.

good luck and have a nice day

Product owners are free to have their own stores, launchers, ecosystems. So many of them do. No reason to cede all that to Valve because Steam is popular.

Or agreeing to sell a product on Steam isn't contingent on giving up on aspects of your business.

Because they are selling their games through various shop and a launcher allows for a unified patching process.
Else you'd have to upload every bloody hotfix to each store, and worst case have to go through some approval process.

An account allows for cross-platform progression/matchmaking and DRM (i.e. buy the base game at Steam, DLC at Microsoft store, claim some free stuff via the publishers own store -> have it available everywhere).