Because I had a good experience with KDE on SteamOS.

This whole system is setup as a SteamOS-like experience using Jovian-NixOS (I wrote about it here: https://kokada.dev/blog/from-gaming-rig-to-personal-computer...).

Still, as far I remember SteamOS is still on KDE5 and uses X11, while I am using KDE6 on Wayland. So not exactly the same.