I guess if everything just worked, that would be fine, but as of now they don't have drivers for wireless Xbox controllers, so you are stuck installing them manually after each software update. Plenty of software just plain isn't available via flatpak, so you have to reinstall it every software update as well, since anything you do via package manager gets deleted each time it updates.

I just don't think they can predict everything that someone might want to do, which is why additional software exists.