Sometimes users and your help-desk would appreciate if they could keep their previous version, when they decide to uninstall the latest version.

Your application, how well tested it is, cannot foresee all situations, and there is always a risk that your new version does not work for some end-users.

When you set this check box your end-user can uninstall to a previous version

When your end-users use your application on a daily base, in a production environment, then they are depended on it for their work, this can produce an uncomfortable situation for your end-users, your help desk and your company. 

LizaJet Installer has the essential capability to uninstall to a previous version. Just by setting a check box you present your end-user with this essential functionality. The end-user can uninstall only the latest version, and restore the previous version of the application