Cat owners know that they are the perfect pet, except for climbing the curtains, skewing the upholstery, waking you up early, and knocking everything into the floor from any elevated surface they can reach. Why do they do that? Are they jealous of any possessions their human might like? Are they doing it to piss us off? Or is it to exert dominance over their environment? The answer is simpler than any of that.
It shouldn’t surprise you to learn that cats knock stuff over because it’s fun. That’s it—that’s the whole explanation. If you want to stop it, you need to know why this particular hobby is so enjoyable so you can give your cats better, less destructive outlets for that energy.
An article at Lifehacker goes on to explain in detail why cats find it fun to knock your stuff to the floor, and more importantly, what you can do to stop this madness. -Thanks, WTM!