I think social skills are definitely required in a game such as D&D. The implication that this leads to a lack of role-play is incorrect. Those who do not wish to role play will not do so, regardless of whether there are game mechanics for dealing with social interaction.
Here's an example: How is a player supposed to accurately role play a character with 30 charisma? Even the best role player in the world would be unable to live up to what that stat implies. Is it fair, then, that because the player cannot articulately debate his point with his DM, Zojan the 20th level bard suffers the same problem when arguing with a peasant?
The argument could be (and has been) made that a good DM will take into account what a character's stats are when interacting with the player. News flash: that is what mechanics are for. Certainly, the rules as written need work: just because a player can get a 40 on his diplomancy check when he rolls a one doesn't mean everyone he encounters should suddenly be his friend. But, better rules can achieve exactly what is needed.
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Player: "I tell the innkeeper that we want rooms for the night."
DM: "The innkeeper looks you over, and tells you that he doesn't have any rooms available for your sort.' "
Player: "Ok.. I tell him that we _really_ need a place to stay."
DM: "Make a diplomancy check."
Player: "I got a 23."
DM: "Hmm.. ok. The innkeeper is so touched by your heartfelt request for aid, that he overlooks your bloodsoaked and travel-stained garments and hands you a key to a room."
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One might claim that the situation described above is pure number crunching, rather than role playing. Well, frankly, I don't think it is fair to expect players playing social characters to possess all of the skills their characters do. How would you like it if your DM made you actually demostrate prowess with a greatsword, before letting your character kill a bugbear?