I think this is an insightful take. My first tablet was 7”. Most phones are 6” now. The extra size of a 10” tablet does not buy much extra functionality and we all basically have “phablets” now. And in the end, these big smartphones did end up taking up 80% of the tasks I used to do on my laptop and I don’t hesitate to leave it at home for a trip unless I know I’ll need to do a heavy creative task.
This is a pretty bad take. The mobile market is much larger precisely because they AREN'T computers. They are mobile companions. But you don't do the same things on a computer and on a mobile phone.
Who edits their movies on a phone? Who codes on a phone? Who writes their PhD thesis on a phone? You will be hard pressed to find professionals who do these things. Because a phone is not a computer.
The main usage of computers even before mobile phones was to browse the web, read and write emails and play games. Web and mail is mostly done on phones now. Not sure about games.
The use cases you mention are much smaller.
Steve Jobs had the right analogy: Tablets are cars, desktop computers are trucks. Few people use trucks. Most use cars.
There is absolutely no one I know who uses a tablet as their primary work computer. No one. That analogy instantly breaks down because of this. As if everyone drives to work primarily using their trucks.
The even more sad thing is that the iPad hardware is absolutely capable to be the primary computer for people. It's simply Apples refusal to allow a real OS to run on it that keeps holding it back.
Young people, the poor, many people in developing countries tend to all be mobile only.
I don't have hard figures but i would estimate the number of people who do all their "computing" on a phone or tablet numbers in the billions.