probably because they are faking it so much. they aren't exactly professional actresses. They have been instructed (but not what specifically as to what to do/say- I'll guess) to over act , be verbal/vocal . what are they suppose to say & do for the audience/camera ? They are not told to just be themselve, or perhaps they try too hard to make a good video. By & large they do a pretty good job IMO. No one is expecting that much but not be bored either.
Men look just as dumb when they are fucking, if not worse, IMO.
I'm sure they dont have to be professional actresses. And i do understand the verbal stuff.. i dont understand the overacting though. I think i would find it more attractive if it was an honest to god sexual experience. If the girls would truly get off on it. I'm sure there are lots of women who do.. but with most you can tell they only play the part.
Men look just as dumb.. true.. but they dont dress-up, don't act orgasms, dont shout like their on fire.