Religion. That fucking poisonous blight on humanity. God goes to great lengths to create us a certain way (apparently), and then has to go to even greater lengths to give us a massive rulebook of genital do's and dont's.

'Right, going to put a foreskin on the penis and then tell them to cut it off! That'll confuse them!'

If that's the case he's a fucking idiot!

Of course, he's not...the people who invented him are :-)