Eeh, I think you're rose-colored-glasses-ing the Steam/Steamdeck thing.
That's absolutely a near-monopoly using their near-monopoly money to make a platform, for a service, to sell you software.
Just because they're more friendly appearing, doesn't mean they're any less interested in lock-in and revenue generation from the lock-in on the hardware that's running their platform.
And just to veer this off before a WELL AKSHULLY shows up: you can run arbitrary software on the Steamdeck, yes. You can also do that on Apple hardware, or in Windows or whatever, and that doesn't invalidate their general business model of trying to be the trifecta.