> Smartphones are not replacing computers in terms of a device to get work done, other than email and phone calls.

That is A LOT of work (real work) being replaced right there.

We also need to stop thinking people bought personal computers to work or be more productive. Part of the personal computer market was sustained by families needing a device to be connected, browse the web, do homewrok, etc... those use cases are now being replaced by the phone or a tablet.

Nobody is saying that smartphones are replacing computers completely, just that for a big part of the market the computer was a complex tool that was underused. That market is now finding smartphones/tablets are simpler to use and more apt for the tasks they want. We will always have specialized devices for certain jobs, but the main computing device is (for the majority of the population) the smartphone.