Have you ever thought about what thought processes go through a cat's mind as they're deciding on a course of action? I can just imagine what my cat Hercules was thinking before he laid down as shown in this picture:
All I can figure is he must have thought, "Oh, look, that human who feeds me is staring intently at that horizontal collection of papers. Since everything in the world revolves around cats and their needs, he must be looking at it because he wants me to sleep there. OK, because he feeds me and scoops my poop, I'll humor him this once."
My daughter reports he does the same thing to the keyboard of her laptop.