If a human is tired, they still try to maintain a sense of dignity. They'll stifle their yawns, keep their eyes open and stay upright until they can plop down into a bed. Cats, on the other hand (paw?), couldn't be bothered for such games. For a feline, the world is their mattress.
As fun as it is to watch cats go crazy toward cleaning products, I'm not sure they have much room to complain. Do they have clean up a box full of our poop? I didn't think so. The defense rests.