Newbie has a question why show 1080p on a native 720p screen

[Got2LoveGadgets]

Hi im new to this site and new to the world of Blu Ray. I have a question which I hope someone can answer (not stricktly a Blu Ray question). Why output a 1080p image on a LCD or Plasma with a native resoulution of 1280x720 pixels (720p)? I have been doing some testing at home on my 32inc LCD which handles a 1080p signal but is not a full HD set. I downloaded using my PS3 two clips of Ratatouille one at 720p and one at 1080p and I can't tell any differenc in quality when playing them back. So in short my question is why do new LCD's make a big thing of being able to handle 1080p if they are not a full HD set? Because as far as I can tell it makes no differenc to the picture quality.