Because when you're a kid, there's nothing better in the world than getting outside and splashing in the puddles.
Darn those well drained streets, though, because our puddles weren't very big. The little one still managed to be soaking wet. They found dirt to make a soft landing for when they splashed, they used pebbles to make campfires and grass clippings for a soft bed. It took a while, but they did discover how fun it is to splash an unsuspecting sibling.
Life is good.