I can see how 'authoring from your lap' with a laptop actually on your lap (while on the sofa - like I am doing right now) might benefit from bigger/multi screens instead of the tiny portal the laptop gives you, but as soon as you want to do something more complex probably you'll reach for your mouse, and perhaps a paper and pen/pencil (if you think with your hands). Thus to the desk you go, where all your monitors are anyway.