I dunno... I'll often leave credit for a free drink for a server after work if they're having a crappy day to cheer them up, and I never leave my name on it. Sometimes you'd rather not attach the "by the way, I'm responsible for this" to things you do to make people happy, because it's supposed to be able making someone feel a little better about life for a couple minutes, not about what a nice guy you want them to think you are. So I don't think it's that weird. Could be a girl, for all you know.