It can be fine to just "talk it out, man", but that runs into the problem where my character on paper has CHA 20 but me in real life rocks a solid 10 CHA. Or the other case, where the fighter with 8 CHA has a salesguy for a player, and he punches well above his on-paper skills using his real life personality, where I'm sidelined.
There is another. I've found that being (imo) charasmatic, and being a charasmatic character, means DMs just talk to me, rather than ever asking for any rolls. Sure, my argument is convincing, but I still want to use my numbers!

-Isaac Asimov, Foundation (1951)