The problem is installing always takes at least two steps: Add repo, install package. Maybe even a third: Verify/add key.
Snaps are usually published by the official upstream, not by Canonical. The Snap store allows them to upload their binary packages directly and immediately. That means you get the latest official releases without having to find out where to get the latest official releases.
Isn't that the same as apt and PPAs?
yep indeed, so to me (but I don't know if I'm interpreting all this correctly) Flatpack seems to push towards a PPA like system for distribution but with a SandBoxed App over one or multiple Runtime for execution
This is something I particularly like about FlatPack. I hope we can go towards a decentralized package distribution system where the app store just has a list of official flatpack repos. You update the latest Firefox from the repo at mozilla.org, the latest Blender from blender.org, etc... of course this needs mozilla, blender.org, etc... to package the app (but they already do it for win, mac and .deb anyway). So you always have the latest version and it is provided by the official website and not a central Canonical repo