This kind of lock in is even less relevant now with cross platform play and similar options becoming a common game feature. Take a game I play, Dead by Daylight; people can add friends on PlayStation and Xbox through BHVR (the dev) ID. It takes some work on the developer’s part, but they can provide their own tools to break that Steam lock-in.

So let’s say some public corporate emergency prompts a Valve exodus (eg, Gabe eats babies) - people would need to buy new copies of their most played games, but in many cases their account progress is on a movable ID, so it wouldn’t even be a huge blocker.