I was reminded of this topic that I have ranted on before by an (apparently) off-handed comment by Mr. Novak from a post on Secrets from Turn of a Friendly Die.
"...For the same reason I don't like players in, say, GURPS, taking an advantage like `charismatic' if they can't play it."
There are a number of folks who feel that you must roleplay all your social encounters, and yet that it's perfectly reasonable to simulate combat with dice.
Trust me, I, personally, would be much more able to convince you of something while holding a six foot battle axe in the crook of my left arm, than I would be using my words alone. Even with my notorious poor luck at rolling the correct numbers. (Which is why my, "No kidding! There I was," dice stories are so rare, and so outrageous.)
Oh sure, there are times my charisma's turned on, and I've got the mojo, but those are noteworthy for their rarity. The truth is, I'm a much better fighter than I am talker, in real life.
...but I'll play a Fiona. I'll play a scheming, manipulative, balseraphic, talker type when I game. Because when I game, I'm playing someone I'm not... so I don't think it's fair to expect me to lead the crowd in a rousing speech myself, even if it is "in character."
Not unless you want me to defeat you in a contest of arms next time I kill a kobold.
(Alright, truthfully I've met gamers that would wipe the floor with me in any kind of physical contest, but the point's still there to be made.)
Epoch had this to add in the original comments...
This is an issue I can see both ways.
The real matter at hand is one of the most notoriously far-ranging and intrusive animals on the gaming landscape -- a fourteen point stag that I call "Immersion in the Game World." Many gamers make seeking this stag and putting his rack over their mantle a big goal. For some, it's the entire reason they wander the gamescape.
If you want to seriously hunt Immersion, you generally want to try to minimize things which pull you up to the game level. You spend as much time in your character's skin as possible.
Now, sometimes, game-level stuff is required. You can't handle combat in-character -- the safety of the players demands that it be abstracted (plus, your GM's probably not able to physically occupy the positions of a half-dozen kobolds at once). Even so, the Immersion-hunter will want these kind of distractions minimized -- if possible, the GM will handle the mechanical details, and they'll interface with the game system on a wholly descriptive level.
Dedicated hunters of Immersion are intolerant of what they see as unnecessary jumps to the game-level. It is, after all, conceivably possible for you to talk through your con or fast-talk or inspiring speech action. It endangers no one. You should at least, they argue, give it a try, because it's disruptive to all Immersion hunters' game experiences to have to go to the dice (or the mechanics, if it's a diceless system), and it makes their response harder for them to formulate.
Let me expand on that last bit. Most dedicated Immersion Hunters follow a style of characterization which we might equate with "Method" acting. That is, they try to sublimate themselves and think as the character. This is enormously easier to accomplish if the stimulus for character decisions comes to you on a level that your character (rather than you, the player) can interpret. Thus, hearing an inspirational speech, you can latch onto concepts which inspire your character, or concepts which don't inspire your character, and react as your character would react. If you hear, "He got a 17 on his Leadership check," then you have to somehow translate that to an IC speech before you can react to it from within your character's skin. Further, your friend Bob might translate it differently, and then you've created a discontinuity in the game world. This is bad for the Immersion hunters, because it could create another break from immersion later on.
Immersion Hunting is one of the commonly advanced arguments for "no cross-gender players," for the same reasons: it's disconnecting from the game world to have a big bearded guy with a bass voice acting the part of a lithe elven lass.
I said that I could see this both ways, and I can. I like Immersion. I sometimes practice it. But it's a very disruptive style of play if not everyone at the table is on the same page. Ultimately, a table of Immersives work well together, and can come up with some truly intense play. But sometimes, it's both more fun for me personally and the group at large to take a step back from that, and play things more on the game level. That allows us to "stretch our wings" and play characters whose skins we couldn't really get into, and it lets us play the game with minimal problems if someone else doesn't feel like going for that 14 point stag that night.