Overheard an exchange earlier between a man and his very young daughter, in a supermarket car park:
Man: we're just going to wait here for a while.
Daughter: why?
Man: because mummy's in the shop.
Daughter: why?
Man: she's buying some chocolate.
Daughter: why?
Man: because she needs some.
Daughter: why?
Man: *laughs*
It was a laugh that said "when you have your own bloody children, you'll know".