I'd hope this community of all places would understand that "just integrate X with Y" is never as simple as "just". It's still something a team needs to do, and the gain is minimal unless Epic is also going to try and make their own console-esque device. That's the incentive for Steam.
Valve started this to have a path towards independence from Windows, just in case Microsoft had locked things down. Not for making devices.
The same rationale exists for Epic, and they have spent an enormous amount of resources fighting Google and Apple over this.
I think it's an ideological decision rather than a technical one.
Going by the Steam hardware survey, 3/4 of Linux users were not using Steam Decks when they got polled. So I’m not sure if a console-esque device is actually required. A large part of the reason why Linux usage is growing, is probably that it mostly just works these days
https://store.steampowered.com/hwsurvey/Steam-Hardware-Softw...