It was because these templates uses the show_menu2 module:
You need to modify the PHP files of your template to call show_menu2 where you
wish to have the menu displayed. Remember when you replace calls to the old
menu functions to use the new parameters that show_menu2 requires. "
I installed the show_menu2 module, and now these templets works fine.
This could be a bit confusing for newbes like myself. But then, this is the first confusing thing for me about this CMS so far.