Hmm, you have uncovered a problem with both of our ideas. Steam’s leverage is reduced after they have deposited sales proceeds, and is gone after the publisher isn’t selling games on the platform any longer.

(I’m griping about Rockstar specifically but my point is still flawed in the general case.)

Now punish publishers who try to change the terms of sale after sale. “Want to play the single player game you bought a decade ago? Agree to this new arbitration clause.”