Why do gentlemen let ladies go first?

A general, cynical observation to follow. I'd like to think that most males are instructed by their parent(s) that men are supposed to treat women a little more special. This may be old-school thinking, in this day and age of equality. However, I do believe that women enjoy a man paying for their meal, opening a door, and letting them go first. Well, having grown up in the "me" generation, I do believe that men of this era do still adhere to those gentleman's tenants. However, the "me" stands out when you let women go first, because you can stare at their ass as they proceed in front of you.