A big reason is the use of a proprietary backend for the Snap Store.

Ubuntu is hiding stuff. And FOSS people dont like it.

The rest of the linux world has embraced flatpaks instead.

But ubuntu wants to do their own thing.

Competition is good though.

Imo, if you are concerned with privacy and freedom, use a distribution that uses flatpaks. Like Arch, fedora, or Linux mint.

If you just want your computer to work, Ubuntu and Snaps are fine.