Do you just simply uninstall it from the Android settings? On desktop, when you uninstall and app, it most likely leaves files and directories behind even if they are hidden on your system.

When you uninstall and app on Android, is this also the case? Or does it also delete every single file and directory associated with the app?

Some Android apps (very, very few) Will create files in your Documents or Home directory and I understand these will not be removed when you uninstall an app.