I think part of that is because of its form factor already limiting the device. Like how Android and iOS are fine on a phone or tablet, but I doubt most people would want it on a desktop computer.
Not talking about the Linux part, but the real test with the Deck is whether or not it'll stay a target platform with its low performance and Valve not releasing a Deck 2 anytime soon. Valve's Steam Deck verified program already checks performance on games and newer games like Horizon Forbidden West and Indiana Jones and the Great Circle are failing.