So the software gets installed. But then the user sees what it really does and wants to un-install it. Remember, this crap shipped with no uninstaller. So eventually someone was going to have to come up with a "cookbook" method of un-installing it. This was the "problem" that the rootkit was trying to "solve". If you can't see the files or the registry keys, there ain't much you can do about it.
But why would Sony want to prevent uninstallation?
There are criminal penalties lurking in the shadows of any class action suit here.