full range or mini's and a sub

Guys I'm not the most seasoned audiophile so I'm sorry if this is a stupid question.  However, here it goes...  I have heard many audiophiles talk about the magic of mini-monitors and their ability to disappear and soundstage.  Many say that it is very difficult to get the same advantages with full-range speakers.  Still most reference systems seem to be built around full range speakers.  If there is a true magic to mini-monitors why don't I see more reference systems with mini-monitors and subs for the lows?