I have just uninstall WampServer because it did not worked (I had 403 error which I could not resolve). After the uninstall is still see "C:\wamp\" directory. Why?
Not all installers remove all the folders they originally created.
There is a good reason for this - you may value any configuration files you changed that were stored in that folder.
I'm just speculating that this is the reason whoever wrote the installer/uninstaller did it this way. It could also be a mistake, or any other reason. If it worries you, just delete the folder.