I've long considered the tendency of retail businesses to put young women to work at the register rather than in the storeroom or the kitchen a natural consequence of (predominately male) managers' desire to greet customers with a pretty female face. Well, that and a prejudice that women are too delicate for strenuous tasks like unloading pallets or manning a hot grill. But a recent discussion reminded me of the stunning degree to which women in our culture are socialised to be constantly pleasant and friendly in a way not generally expected of men. So even if you were choosing your cashiers strictly on the basis of ability--primarily the ability to be courteous to strangers for long periods--you would end up selecting many more women than men.