Wouldn’t you want them to be in system monitor so you can see how much resource they are using?
I phrased it as a question because it may not be the right decision but seems in line with the Disks one. I think this looks similarly ridiculous:
Perhaps they should be bundled with / and maybe even made expandable from there in some sort of drop down (though that requires developing a new feature)?
snap list gives the size of the snaps but I guess some may not realize that snappy is storing three copies of each snap so the snaps are actually using up triple their disk space size.
How System Monitor handles Firefox multiprocess should probably be cleaned up too…
Could you report the issue on launchpad?
That looks like something easy enough to fix and worth looking at (not before feature freeze though)