It’s really hard to type with a cat leaning on your hand. For one thing, you don’t want to disturb him because he purrs so sweetly. You don’t want to disturb yourself because the softness of his head feels so nice. And you don’t want to risk the wrath of claws.
It’s not like a sleeve you can cut off, either. It would be a bet messy if you tried to do that to your hand, and besides, even if you could without disturbing the cat, you would lose to ability to type.
This makes the whole idea of trying to write on a laptop computer rather futile with a cat around, because in his opinion there’s only one kind of appropriate laptop. So it’s okay that I’m not doing anything, because I have an excuse and he’s sitting on me.