None of that matters, honestly. The expectation is more that you go out of the house with a happy face. If you work at a store or in other customer service fields, it isn't enough to be nice and polite, you need to smile as well. I worked in a call center and we got told that we should smile while on the phone, even.

And sometimes, the order to smile is some odd sort of thing men do to women, especially older men to younger women.

All of it becomes habit.