This is my new theory. Cats think that laptops are robot cats. Or sort of minimal machine-cats.
They are warm
They sit on our laps or bellies
They make a low, gentle noise
We nicely pet them all day long
We give them long strings to play with
There is often room on a human's belly for a real cat while the robot cat gets petted
If you are a cat, and stare at them long enough, the real cat might come out.