It is difficult to match productivity on a phone when compared to a computer. No one can code from a phone or do similar work such as graphic design. What if you could be working on projects directly on your phone?
Specialized apps that focus on particular uses of a computer that phones are not currently used for.
A phone could be a touchpad. Why use a mouse or pay for expensive pads when we have touch screens we use every day? A code editor or note pad that is faster than a computer.