I think for app uninstallation to be relevant it's not whether the app resides on disk that's important, it's whether it's interfering with how you use the system. E.g. for a browser it's just important that the browser isn't registered as the default browser everywhere, but you can install your own browser. Being able to "uninstall" an app in a relevant way means being able to make it appear as if you don't have it. Whether or not the files the app uses are still on disk is perhaps relevant for disk space, but from a legal standpoint that seems almost irrelevant.