By default uninstalling Jomres does not affect the existing Jomres tables, this allows you to re-install Jomres at a later date whilst maintaining the original data.
If you want to completely remove Jomres altogether you will need to visit Jomres > Settings > Site Configuration > Misc tab. In there is an option "Delete all Jomres data when uninstalling?". Set that option to Yes and click Save. Once you have done that then you can use the CMS's uninstallation process to uninstall Jomres entirely.