I agree with you. I know my first teacher used to hum or sing quietly deliberately--he told me I would dance differently (better) when he did so. To me, it's charming...assuming it's done relatively well. I tune in more to my partner, it feels like he's more in tune with the music...when I stop myself from humming along (because so many people seem to dislike it so intently) I actually find that (the deliberate stopping) distracting. I can hum and dance at the same time--it's two simultaneous expressions of the music...it's like I can't keep it to myself. Sometimes, I'm just moved enough that I want to hum or sing along quietly...which I can do and dance at the same time just fine...but suppressing it is distracting.