This is really the only answer. If you think being able to put your your desktop in your pocket and use it anywhere would be useful, then you'd probably find a smartphone useful.

Plus, with the right combination of applications (more preferably, a few, and some with no active internet permission at all) and power settings tweaked both for better battery mileage and longer, more focused on-the-go sessions (e.g. editing documents, playing that one dungeon crawler roguelike, and planning important events, etc.) you could count on it more.