MUs have a /social/ aspect to them. At no point in MUing am I actually karate chopping people or performing heart surgery. I am talking to people all the fucking time, though. The social aspect of MUing also tends to determine if anybody enjoys spending their time RPing with me. That's kind of important. Your RL kung fu or medical knowledge isn't particularly relevant to me enjoying the 5 hours I spend RPing with you unless I'm some kind of pedant. Whereas people being bad at lying, persuasion, etc, while they're SUPPOSED to be some suave casanova is actually a noticeable drag on writing. If somebody wants to roll brawl dice at me and punch me, okay, I got punched. It doesn't really matter how they pose punching. And punching has no real "effect" beyond the physical damage. If you pose a god awful bit of persuasion and succeed on a roll, I now have to write a handful of poses of my character falling for garbage.
It's just the way things are, and the way things always will be. Because we are not just playing a game. MUing is not a video game. It's a collaborative writing experiment. Understanding social dynamics and how to make a pretty turn of phrase or write a convincing argument is a hell of a lot more important than how well you can describe punching somebody with the exact realistic amount of force needed to break their nose and shove bone shards up into their brain.
This whole "we don't expect people to actually be doctors! we just let them roll medicine, so we should just let people faceroll across the keyboard and roll dice for social interactions!" just seems daft. Social interactions are more of a give and take thing. A fist fight is just a 'versus' thing. A medical roll is just 'do you succeed or not'.
It's one of the more pointless recurring arguments around here.
Playing with incredibly socially inept people just /is not fun/. Even if your game lets them roll dice to make up for it, they will quickly wind up ostracized on account of not being a fun RP partner.