To some people. I have an Air. I love it. It's small, It's light, It can fit anywhere. It takes up about as much room as a folder in my backpack, which is awesome for air travel, the more I can get in my carry ons, the less I'm paying for baggage.

When you've got to carry it, yes.

YES. It's a laptop. If you can't sacrifice the screen size, where else do you trim the fat?

thinner = less mass = less weight = portability. A laptop is designed to be a portable machine, no?

Desktops however, I do not care if there is a massive tower under my desk. I don't move it unless I'm plugging in something new, or upgrading components.

No, unless you carry it around a lot, at which point durability is more important than thinness resulting in thinness not being important.

So ultimately, no it's not regardless of the use case.

You know we are talking about laptops, right ? By definition they are supposed to be portable.