We usually stay on the safe side so we do not remove JEvents tables when uninstalling just to prevent user uninstalling by error.
What you can easily do is to remove all JEvents Events and categories, then uninstall and finally remove all tables from the DB.
Also, JEvents performs an orphan search of events after upgrade or re-install so that might be also a good thing to check after reinstalling (go to JEvents CPanel to check any message)