At least the steam method is fair. I don't expect to be able to run one copy at the same time. Just to be able to install games on both machines and be able to play one instance on either. Seems to work fine until games use their own DRM.
I completely agree, there's no harm in my view as long as the game is only in use on one system (or account) at a time. We already lost the ability to resell PC games many years ago, the least they could let us do is "share" games.
My Mrs and I are both PC gamers who mainly play single player titles. We've just had to accept that we have to purchase two copies of anything not on Steam. It means we're much more selective about purchases now.
Many years ago - 2008 IIRC - we played through the Rainbow Six Vegas 2 Co-Op campaign using a single disk which was awesome. Good times.
Back on topic, I'm actually enjoying Watchdogs 2 far more than I thought I would, and although when maxed out it struggles at least the game's options make it scalable.