I agree with OP. We do have an age feature on the profile that updates every day so that we don't have to make a topic whenever it updates, and quite frankly birthday threads are annoying. Tell your friends about it on steam, nobody else really cares.
And, yknow, you guys are right. It doesn't hurt anyone! It doesn't really do much damage at all. But you could say the same for spam/stuffpost topics. If I make a topic and all it says in it is "My ass itches", it wont do any damage to the community whatsoever. It holds about the same amount of intellectual content as a birthday thread anyway. Where do we draw the line? Personally, I think all threads should have some form of actual content that can warrant a discussion. That is the definition of topic, after all. Birthday topics will push other more valid topics down the list, and it's kinda bullstuff.