Steam trained a whole generation of gamers not to expect real ownership with resale rights. It's sad. The population old enough to even know this is how it used to be is shrinking.
If Steam/Valve decides to turn evil one day, it'll be trivial to just pirate whatever game you want to keep playing on the PC. Not to mention that Steam already allows you to backup all your game files if you so wish.
Steam won because of convenience and all the other features they bring to the table like the community markets, guides, achievements, cloud saves, Steamworks for lobbies/friends etc. Like Gabe said himself, piracy is a service issue, so if Steam itself enshittifies things will correct themselves, which can't be said and done for a closed platform like Sony/MS have.