Yeah its made very confusing. For example, they use language like "Purchase for myself, purchase as a gift" when you go to buy something. Purchase is very specific language and is different from a subscription.
With Steam we are dealing with 3 things: Steam, the game license, and the game. You have a free "subscription" to Steam, which is your account. It has its own agreement. Steam then sells you a game license (again with that "purchase" language) that allows you to play the game. The game has its own EULA. As part of your Steam subscription they let you download the actual game files so that you can play it with your license.
If you no longer agree with the terms of your Steam subscription, what happens to your paid for game licenses? Technically shouldn't you have those still since you still agree with their individual usage terms and have paid in full? Maybe Steam doesn't have to serve you the files anymore but you damn well should still be able to play.
Really its going to take a court case to decide digital property and what all this shit even means. With so many people buying digital content on a wide range of services its only a matter of time before it gets decided.
I mean the alternative scenario for Steam is that they don't ever sell you anything. Steam keeps ownership of the game licenses for itself and gives you a one time payment to access their games, which they can revoke at any time. Essentially we are simply borrowing from Valves vast game library.