It's because children are actually energy vampires. They steal energy from adults and use it for themselves. True story. How many times do you see gatherings of adults and kids and the kids are running around like crazy and the parents all look sucked dry? I rest my case
Last night I walked away from the kids' bedroom for a minute, only to return and find my 4 yo daughter teaching my 2 yo son to climb up on top of the chest of drawers and jump off onto the bed.