i think its to do with nakedness. why would you want to sing a song in public that you didn't know. in a way it makes no sense.

but people have a need to expose themselves as something more than a societal unit. they need to stand tall ....its harmless. its healthy even..self expression....   a sort of emotional naturism.

it does lead to some strange sights though. one place i used to go occasionally. a bloke used to get up to the mic. hold up a piece of paper and read (not sing) the words of CrystalChandelier - like a shopping list.

i often wonder what he got out of it - what he expected us to get out of it. still, it must have fed a need inside him, and it did no real harm.