[benoau]

Some of them do, the Total War games I play the most require weekly online activation.

But that's just using what you payed for, it only very slightly overlaps with what actually owning something entails.

[RHSeeger]

Is that online activation Steam or is it a third party thing? Steam allows selling games that have external DRM like that. I think they, themselves, don't do it.

That doesn't invalidate your other point.

[Macha]

Steamworks, the integration library for games to interact with Steam features, has an optional DRM component. It's not a particularly impressive one, so it's more about stopping people copy/pasting their steamapps folder than stopping dedicated pirates, hence why so many publishers use alternative solutions.