I am no expert on this subject and to get the full benefit of the cha modifier a roll needs to be made. But, say your char (from above) tried to convince me of a plan of attack. It could be a really good idea but your low charisma, makes you hard to listen to seriously. You have a hard time getting your points across and I (as a pc in general) am more inclined to hear what the guy/gal with a high charisma score has to say.
So your character comes up with an idea. no one really hears you. The Bard (with high Charisma and int, maybe wis) hears you and gets everybody's attention and repeats the plan. hmmm, that bard has a good idea.
this is my take on it. To have this work rolls need to be made though.
I also am of the school of thought that a charisma score has a little to do with looks. But it is race specific, A beautiful orc is beautiful to other orcs but still ugly to a human and vice versa.
Etin