snap backend is proprietary and controlled by canonical also people don't like the slow start up times
There are better solutions for everything it does/tries to do:
It automatically updates the software you've installed, and there's no way to turn that off. That's why I personally hate it.
One thing really annoying for me, there's only the 1 official "store" you can use and it doesn't support ipv6.
https://wiki.ubuntu.com/IPv6 says it's been available for apt since march 12th 2013.