The form factor is useful for a lot of application. My laptop/desktop is more powerful, but they are limited to places where I'm sitting down. There are a lot of jobs that are better done walking around. Trying to fix a machine - you want the computer with you. Trying to do a presentation - your presentation is better if you are not standing still.

What is serious computing? There are some things where I expect to have to be at my desk for hours to get them done and then a phone/tablet is worse. However there are also a lot of things better done when not at a desk and a laptop/desktop is worse.

“Serious” computing would be using several applications that chain together to create an end product.

Case in point: authoring academic papers. If you have a local or self-hosted Zotero collection, you will want to cite them. Any desktop platform allows you to use [word processor of choice] and Zotero together fairly seamlessly.

This is a big kludge on iPadOS where you keep switching back and forth between Pages/Word and Zotero to paste in a citation key, which then makes it untenable long-term because the attention break is too great.

For simple tasks (someone pointed out a rental car agent doing the walk around photo taking and signature capturing) an iPad is great - its light weight is the main advantage. But if I was doing a walking-around task that was more complex, a convertible laptop that folds around (HP x360 for example) and runs a real OS is just more powerful. There’s nothing an iPad can do (besides being light) that wouldn’t be done better by such a device. (Assume here that Apple made an x360-shaped Mac, this argument isn’t about Windows vs Mac).