I agree with you that Apple doesn't directly profit from building an upgradeable machine. But from my perspective, upgradability is one of the factors that affect my purchase decision--part of the value for the package, if you will. My current computer is a 2014 MacBook Pro, so I look at it from the laptop perspective.
I am not a power user by any means, so I don't need lots of raw computing power. To me, the values of owning a MBP is design, build quality, good compromise between weight/power, OS X, and longevity. However, longevity is reduced by removing upgradability for RAM and SSD. I don't see MBP as attractive as before, especially with the price premium. I admit that I am cheap, and I try to spend as little as possible. I typically get the lowest spec'd MBP that fits my current need. After a few years, I upgrade RAM and storage (used to be HD, now SSD), and that will last me another few years.
Apple's current offerings doesn't fit my need, and I am exploring other alternatives (currently test driving Asus Zenbook 305 running Xubuntu alongside my MBP). I am not bitter, just disappointed since I much prefer Apple laptops.
Also, the lack of reasonably priced SSD upgrade for Retina MBP due to proprietary interface is driving me nuts. I am running out of storage space and can't do anything about it.