The NavBar uses Twitter Bootstrap and the effect you're seeing was designed by Twitter intentionally to allow the menu parent to open the child list only. If it was linked, it would open the destination link instead of the drop, since the menu doesn't use hover action to open that list. We recommend that those seeking to use NavBar create a destination link in the child list.
Alternatively, you may also use in place of NavBar the Nav Classic menu via Drag & Drop > Header.
The Nav Classic may be styled as you wish via CSS and uses hover action for opening the child list, therefore the parent links can be linked elsewhere. It does not, as a default, have the same appearance as the NavBar and it would take some effort to make it do so.