Honestly? I think Charisma shouldn't be an ability score. If we'd prefer social negotiation to be role played and not to be "roll Persuasion against made-up on the spot DC" (or worse, not allowing rolls at all, because c'mon guys, nobody would be so gullible as to buy a bridge", completely ignoring how gullible real people are, lol), then why do we even have a social attribute?
I'm of a similar mind when it comes to Intelligence or Wisdom- players are going to use their own intellects even if they try to "dumb it down", and some forms of play (puzzles & riddles) actually encourage that, and not many will be happy with a puzzle being solved with a quick die roll. I praised Earthdawn for having Perception and Willpower as stats instead, though they weren't brave enough to bypass Charisma (though at least they tried having a social combat system).
I mean, it's like some people want there to be stats to rate certain qualities, but they don't really want those qualities to be used for anything beyond saving throws!