You don't need to have a subscription to buy or play your games.
Without a subscription you can stream the games you buy at 60fps 1080p with stereo sound.
With a subscription you can stream the games you buy at 60fps 4K with 5.1 surround sound.
There's a risk that they increase the subscription price and hold _higher quality_ versions of your games hostage. Or, of course, there's the suicidal option of changing their pricing entirely such that free users can't stream the games they've bought (because what are you going to do about it?), but I'd imagine they'd shut down the entire service before trying to pull that off.
Without a subscription you can stream the games you buy at 60fps 1080p with stereo sound.
With a subscription you can stream the games you buy at 60fps 4K with 5.1 surround sound.
There's a risk that they increase the subscription price and hold _higher quality_ versions of your games hostage. Or, of course, there's the suicidal option of changing their pricing entirely such that free users can't stream the games they've bought (because what are you going to do about it?), but I'd imagine they'd shut down the entire service before trying to pull that off.