I think the distinction being made is that something for casual use (like a Chromebook, or an iPad) doesn't really carry with it the expectation that you will be repairing or upgrading components - if something fails, you replace the whole (relatively cheap) device. For a machine that has a pricetag in the thousands, not hundreds, of dollars/euro, that isn't a very appealing approach...
Hopefully you'll have Apple care, which will allow you to replace the whole machine without paying for an entirely new one.
If you need it for a living, it's a no brainer. Is it malfunctioning? Take it to an Apple store, grab a brand new device, restore it from Time Machine and resume where you left off. You could be back up and running in a couple of hours as if nothing had happened. You could potentially waste a lot more than that trying to troubleshoot and then ordering new parts.
That only works if you have good Apple Store coverage though. Otherwise, the table flips.
That's also a reason to make it less repairable. If you can replace parts with aftermarket parts, the gray area of applecare support is much bigger.
People who are using these computers "professionally" mostly don't want to fiddle with modifying them. They want a computer that will be reliable, and whose failure will cost them the smallest work interruption.
Fair, though it doesn't take a very cynical mind to also see that there's a benefit to Apple if I can't double my ram in a couple of years, and instead have to buy a new machine...
