Isn't it in a read-only partition, where, by definition, you wouldn't be able to reuse the space? Wouldn't it only be users at their storage capacity who would be affected?

The fact they they are installed in a read-only partition is what makes them non-removable, if they were installed in the regular partition then the "system" partition wouldn't need to be so big, they would be removable and you could reclaim the space.

Then you couldn't factory reset without access to a network, as I pointed out.