I don't see the relation between sandboxable and unremovable.
The argument for making some things unremovable has always been that their absence leads to a broken system. I can see how that applies to gnome-software (can't install apps anymore when it is missing) and to yelp (every apps help menuitem is broken when yelp is missing). But I don't see how this applies to gnome-screenshot (as Florian pointed out, the keyboard shortcuts for sceenshots don't rely on it anymore) or to nautilus (no icons on the desktop in GNOME3).