I think you are looking at work horse distros, like Ubuntu, Fedora, etc.. That by now are heavily used for productive work, not personal use. So they favor stability and minor quality of life improvements over shiny new updates.
There's plenty shiny new cutting edge distros out there that are innovating, e.g. Nix, Silverblue, VanillaOS, all the container focused ones CoreOS, Container OS, Flatcar Container Linux and probably dozens more newer ones I am not aware of .
Probably because 3rd party app stores can't install apps like the play store can. you need a rooted phone or flash them as a system app to get the same functionality as Play Store. which isn't something your average Joe will do.
On a normal unmodified phone you have to manually confirm each app you want to install. so no auto-updates in the background etc.
Congratulations 🤠🥾er