The contributed pack files are installed by the plugin in the \profiles\[profie_name]\QuickMapServices\ folder.
When the plugin is uninstalled, such folder and the files inside it are not deleted.
I think it should be more correct that the plugin installed the contributed pack files under the plugin installation folder \profiles\[profie_name]\python\plugins\quick_map_services\ or that the plugin uninstallation procedure taked care of the deletion of the \profiles\[profie_name]\QuickMapServices\ folder and its content.