Although, of course, it’d be cool if Steamworks would work for non-steam games at least for modding/multiplayer.

That’s the point. No, nobody’s forcing them to use Steamworks (especially since Epic has rolled out their cross-platform, store-and-OS-agnostic free competitor to it), but anyone who chooses to do so (which is a lot of devs) ends up locking those features to Steam (barring a ton of extra work for themselves) simply because of Valve’s chosen policy.

Don’t think Valve doesn’t understand this. They found a way to get devs to all but lock their games to Steam and thank Valve for the opportunity to do it.