I have been waiting to upgrade, too, but Apple has continued their pursuit of thinness while abandoning the "Pro" market -- specifically professionals using Macs for computing rather than as a fashion accessory. The value and longevity of Macs has decreased significantly from Apple's neglect of both their laptop and desktop product lines.
While most Mac owners won't need to upgrade RAM or disk, I have done so on every Mac I've owned. I don't care about thinness or weight as much as function, compute power, and storage. I have nearly no reason to buy a computer with a slow CPU, small screen, or small SSD, yet Apple relentlessly offers non-Pro computer specs lately.
Phone and tablet revenue have so eclipsed computer revenue that Apple is financially allowed to offer dismal upgrades without recourse. I can only hope their recent Mac sales declines will be analyzed as Apple's own fault, as there are tons of folks desiring to upgrade to a more powerful Mac product.