They could make them literally the same code. It wouldn't kill it completely, but it'd stop some as it could be an attack vector to gain control of a Steam account.
I know you're not making this argument, but it's a good jumping off point for something I've been rolling around in my head. We've had versions of this discussion for a few months now and I think it really comes down to a failure in the community to use the appropriate terms.
Steam, Xbox, Playstation, Nintendo are platforms.
PC, Xbox One, PS4, Switch are hardware.
It's confusing because, in the case of the consoles, the platform and the hardware are inseparable (Microsoft's own efforts to decouple the Xbox brand from specific hardware and expand into the PC market notwithstanding). While there is R&D costs associated with hardware, there are also costs associated with platform development -- and Valve incurs the most costs out of anyone on the PC. Hell, Steam is the most robust and feature-packed platform in gaming right now, period.
And while we could discuss how Valve has entered the hardware space before, with its efforts in VR and the Steam controller that have R&D costs just like any of the consoles, their main business is the platform. It's just about their only opportunity to make money. Whereas the platforms that also have dedicated hardware can theoretically make money a number of times through hardware and accessory sales, licensing, etc.