I bet the 98% of rMBP owners who will never upgrade their SSD appreciate the size reduction instead.
Now if we talk about this particular upgrade, how many people would pay $600 bucks for 960 GB of space, I can imagine it's an even smaller fraction.
The size benefit is something that everyone appreciates when they buy a MBP retina. There are enough other laptop choices if you want upgrade-ability and repair-ability, and MBP retina doesn't need to compete on that level.
Also, you're off by 2%.
Pro is a badge. Just like "Super Deluxe", "Extra Special", "Custom Ordered"..
We don't go around saying that a super deluxe cheeseburger is only for the super deluxe among us.
In actual fact, of course, it implies nothing, and that's why it means none of the above. "Pro" is just a badge, as meaningless as the "Sport" that adorns my car (4 doors, diesel engine).
These days, though, the quadrants are gone, and the names are mostly just branding fluff.
Also, just because professionals aren't hardcore computer nerds doesn't mean they don't desire to upgrade. In particular, creative professionals (graphic artists, video editors, musicians) can always make use of more storage and performance, and in days past, many of these non-nerds would become savvy enough to upgrade whatever they could. Hell, even my parents know what memory is, and that more is better.
It's Apple's product line, they can do what they want. But as a result of their decision, many power users are clinging to the last-gen product line, because it's still upgradeable, and a truly "Pro" Mac laptop is no longer available for sale. (Technically, you can still buy the old form factor, but we all know which way the wind is blowing.)
That depends a bit on your use case. I have heard the Air described as an "executive" laptop, because it makes for particularly good mobility without sacrificing ability to do what an executive type would do- documents, email, powerpoint, etc.
I think that most people aren't obsessed with smaller, lighter laptops, not since the tablet age. A laptop is something you use to sit down at a desk with, and whatever thinness advantage there is goes away then. Apple is losing laptop sales because their line-up doesn't cater to people's needs as well as it used to do.