Unspoken Rules

I have noticed another phenomenon (please reference the "Bag Boy Phenomenon"). Not a new one, but one I believe has been taking place since the wisemen came to see Jesus. We will henceforth call this the "Imbalanced Gift Exchange Phenomenon." This phenomenon transcends all barriers. Whether they are social, religious, financial...it doesn't matter. Everyone is faced with this experience. Here it is:

How come you never send money as a gift to anyone older than you? It doesn't matter if they are 25 and you are 24, it just doesn't happen. However, you are always expected to give a monetary gift to someone below you. Some of you need an example so here it is:
It was my birthday last week, and I received a card with a monetary gift from a few people older than myself. When it is their birthday, they will receive only a card from me. Why? Because I am not expected to give them money. Maybe a toothbrush or a fresh apple, but never money because that might be awkward. I would be in violation of the unspoken gift rule. However, when my cousin Austin sends me a graduation announcement (still waiting...I think his graduation is Saturday) I will be expected to provide a monetary gift (I am almost in the clear on this one, because the exception to the rule here is that if I don't know about it in time, I am not obligated to send money). Who made these rules? How long have they existed? What happens if I am in violation? Who would win in a fight between George W. Bush and Hilary Clinton?

Update: I have included a new link entitled "Website of the Week." This week I am featuring Boxed Thoughts, which I find EXTREMELY interesting. It provides a fascinating insight into people's lives. This site went live about two weeks ago and has grown immensely.