Per your questions to "why remove the registry entries and files during uninstall", from a System Admin's point of view it is sloppy and rude of a software company to leave extraneous files on the hard drive and unused registry entries to clog up a computer after the application has been "uninstalled". Sadly even Adobe recommends a manual removal of files left over after the uninstaller fails to do so in Uninstall Flash Player | Windows but it sure isn't easy to do.