When will I not have to hear old men telling me I should smile? Probably not till I'm old too and they no longer give a crap because my tits will be too saggy. This bus driver the other day acted like I was all depressed, just because I got on the bus and started feeding my money into the machine. I'm not exactly animated on my way to class in the morning. Or any time I ride the bus alone, for that matter. I'm sorry, your bus isn't really that exciting, and your conversational tactic is severely lacking.
I also get this from older male customers at work sometimes. Obviously, as a counter girl, a certain amount of good cheer is expected of me, but if I get a bad vibe off an old guy, I'm definitely not going out of my way. I'll be polite, but that's it.
A significant part of the problem, it would seem, is that my neutral face tends to look like a hostile face to strangers. But that doesn't make it okay for older men to take this condescending attitude toward me, like I somehow owe them a smile. If I have to whore my smile out for a five cent tip, you can take your quarters and shove 'em.
Hell, I can't even tell whether or not I actually smile enough to most customers at all, nevermind creepy old men. I must do something right though, since plenty of people, especially young guys, seem to respond well.
The next feminist revolution should involve us taking back control of our smile.