Or any job that requires creating documents or spreadsheets, managing inventory, and so on and so forth. A small business might start out doing these things on a mobile device, but a some point you just are not going to be productive trying to keep up with these things without a PC.
The closest to using a mobile device for "real work" that I see regularly in the real world are those Square POS systems that are basically just a tablet on a stand with a card reader. Beyond that, it's just things like vendors at a farmer's market or something. Not really high volume.
>No, no, it isn't. Desktop is far more productive than mobile ever will be or can be.*
Only because it has more freedom (to run all kinds of apps, services, etc). Not because it necessarily offers better interactions.
Most people are far better at what they do with their mobile phone, than with their desktop OS.