Especially since, afaik, you plug it in and it just works. No messing around with installing operating systems, setting up users (aside from signing into steam) or anything. It's essentially a console that plays PC games, but it's also a PC for the purposes of upgradability and ability to do other, non-console stuff with it

>No messing around with installing operating systems

This is the real killer feature. So many people that I talk to know they want Linux, but are deathly afraid of installing it themselves.

If you do care about SteamOS, any machine with a reasonably recent AMD GPU will run SteamOS or a similar distro just fine.