Steam is always given an exception in these conversations because they’ve generally behaved - but that can easily change overnight from a black swan event.
Some future manager will look at a graph and think monetization can be improved X% while only losing an estimated Y% of users. It is guaranteed to happen. Question is only if most in the current generation will outlive free access to their entire Steam library or not.
This can easily be changed if Gabe Newell dies, commits a crime, or gets divorced, his estate or trust wants a change in direction, a lawsuit costs Steam a ton of money and they need to get cash quick, take your pick.