I've done some thinking about this, because I suppose both responses are unreasonable (though, full disclosure, I'm more likely to fall into the former camp than the latter). I think it stems from feeling deep in your heart that you're un-cared for. It's a lot more obvious in the first response than the second, but overcompensation is usually an indicator of a lack, no?
The people who comment (and usually the advice-givers) are down on people who think they should be celebrated by their friends on their birthday. "You're too old, stop acting like a child" is how it typically goes.
It makes me wonder what's so wrong with celebrating people on their birthdays. What's wrong with celebrating people in general? We don't have time or energy to do that every day (though maybe we should), but it seems like people should be excited to have one day they can celebrate and make the people they supposedly care for feel cared for.
I'm not talking about addressing the symptom or reaction (sulkiness or self-centeredness) but the root of the issue: that people don't feel like those around them genuinely care about them. Maybe that's not just appreciating someone on his or her birthday, but regularly. Actually caring for people because it's important and because we want to.
P.S. it is still snowing outside. That's six months, folks. And I thought I was going to get to garden soon.