I prefer fake niceties to genuine rudeness. I don't really care what the checkout clerk really thinks about me - if they hate my face and think I am the ugliest lad on the face of the Earth, I'm fine with that - as long as they keep it to themselves and don't bother me. Niceties are grease in the gears of society. I prefer my society well-greased, and if I need some sincerity, that's what family and close friends are for.