Official and picked extensions for current versions
Joomla has very secure and up-to-date core, But extensions on JED isn't official and reviewed by joomla security team, and sometimes updates of new J! comes very lately, and some necessary addons isn't FREE. Therefore integration between core and extensions is necessary. It means official and picked FREE extensions for every current version of Joomla. It is Joomla ultimate !
A missed feature of Joomla .. !