In my mind, really, "role-play" and social skill mechanics are diametrically opposed forces. When I first started playing D&D and other games, we didn't really have social skills. We just...played our characters. I was never asked to make a Charisma check for anything.
There were rules, of course, for encounter reactions and the like based on Charisma, but I didn't understand them and found them to be clunky; it was easier to decide what an NPC's attitude would be, and then have them react to the actions and statements of the characters accordingly. I admit, I was basically short-changing Charisma as an ability, but as near as I could tell, so was everyone else, and we were certainly having fun. One of the DM's I looked up to as a mentor even uses Comeliness in his games to this day, but never once have the mechanics been employed; it's just a number to describe NPC's, so rather than having to say "she's unbelievably hot" he can say "she has 20 Comeliness".
Everything came crashing down the time I played GURPS. Things went well for some time, when one day, we were faced with an obstinate guard, and I wanted my swordsmen to intimidate him, so I roleplayed thusly. The GM asked me to make an Intimidate skill roll (which wasn't even a skill in the core book but in a splat!) and it broke my mind. "Roll a die...to roleplay?" I was flabbergasted.
Thus began my long standing annoyance with social systems. I'll be acting in character, and suddenly "make a die roll". It doesn't matter how sensible my argument was, or how passionately I'm in character; the die roll interrupts me, and even if I'm told I get a bonus, I might get a lackluster roll, and my acting in character falls flat on it's face.
(I know what should happen is that I am asked to make the roll first, then act it out, but it never really goes that way!).
Or the other extreme, the shy player makes a character with Charisma because they want to know what it's like to be liked by most people. They say "uh, i'll try to talk to the noble" and the DM goes "well, what do you say?"; and more often than not, I've seen the DM shake their head and gatekeep the attempt because they can't disassociate the player's roleplay from the character's ability.
Now I have played in systems that go a little extra with regards to social mechanics. Earthdawn had a "social defense" stat in the 90's that I thought was rather brilliant. But when I played 4e, and social engagements were reduced to skill challenges, once again, it became "guy with good numbers wins", balanced by "guy without real life social grace gets penalized."
The way I see it, you can't have it both ways; you either have a game where NPC's judge players by their words and deeds, or you rely on mechanics to determine how an NPC reacts to the character's words and deeds, which may not be the same thing.
Or as I put it often in games "you have to assume the character can be more or less competent than their player".
This is why social mechanics are so simple in D&D, so the players and the DM can find some happy medium that an in depth system isn't going to help, since those can be gamed and optimized; and worse, if they are gamed and optimized, people without good Charisma checks simply won't play, because they know their actions will be counter productive.
Many times on forums I'll hear the argument "ah a Fighter can be a perfectly good face, give 'em decent Charisma and proficiency in a social skill". That tells me that person plays in a game where it's more about the roleplay than the results.
Where someone else might believe that a "face" character is a 18-20 Charisma character with all three social skills (and maybe insight, if your DM believes it does anything) and Expertise to blast past all the checks. That tells me that person plays in a game where it's more about results than roleplay.
Most tables, I feel, are probably somewhere in the middle.