The only reason I can think of is the inconvenience of having to carry a child inside of yourself for all that time, if I were to reconsider my decision about children. The other things I would consider to be in the way can be fixed by drugs and surgery nowadays.
edit: Oh, and standing up pissing is overrated. If not used as an emergency choice when out of options it's kind of worthless.
I'll try to reply to this thread without lacing it with sarcasm. I don't take any more pride in being a male than I do in the color of my skin or any other quality that is completely out of my control. The things I love about being me would most likely still apply if I were female.