Snaps are used for Ubuntu’s IOT distro, and also for their upcoming immutable desktop. They even ship kernel and mesa as snap, which makes updating less likely to break a system (in case of a crash while updating, user error, …).
That’s why they push snap. Canonical doesn’t mainly aim to make a apps available to all distros like flatpak does. Just like now where all distros need their own packages, snap will coexist with other package formats.
For the user it’s unimportant how apps are installed, as long as they’re available.