Why unset permissions every time admin/user/access is submitted?

I don't understand the thinking behind this feature. If all user's permissions to use a module are stripped away, why have the module installed in the first place? Why go through the trouble of hiding it and just remove the damn thing?

I think my ideas for how the module should/could be used are different from the original intent.

It seems as though this was written so that multiple sites could use the same /sites/all/modules directory but permit some sites to get access to certain modules but not others.

My idea, however, is to set up a feature on a site and to prevent an administrator from creating headaches by disabling or enabling a module or creating a security hole by configuring permissions improperly.