I Spilled Milk and Blamed It on the Dog

So I was at home last weekend doing my homework. Dad was busy in his office, Mom wasn't around, just me and Rusty the dog. I accidentally knocked over a glass of milk and it splattered everywhere. Instead of owning up to it right away, which is what an adult would do, I panicked. I quickly pointed at Rusty who was nearby chewing on one of his toys. 'Hey Dad!' I yelled upstairs, 'Rusty got into the kitchen again! He knocked over my milk!' I rushed to clean it up, trying to make everything look like a dog accident instead of human clumsiness. But as soon as I did that, I felt terrible about lying for such a small thing. The next day at school, I couldn't stop thinking about how dumb and petty it was to blame Rusty. My friends don't even have dogs and they never lie like that. So why did I? What made me think blaming an innocent dog would make things better instead of worse?