From the very first Mac, the all-in-one concept has proven to be highly successful. You didn’t have to mix and match computer, display, mouse and keyboard, though the latter two could be replaced or supplemented. The price you paid for the single box was a difficult, or impossible, upgrade process.
The original iMac was said to be a key factor in the Mac’s resurgence for its time, but it was a bear to change memory. You had to open the case, and remove an assembly that included just about everything except for the internal components of the CRT display. It wasn’t hard, but annoying. The same couldn’t be said for several generations of Power Macs that required removal of delicate wiring harnesses to get to the memory slots. I recall when Apple marketing people displayed a brand new model with simple access to memory and other components, and received a round of applause.
After such experiences, I would have thought Apple would recognize that at least some of you may buy the Mac you can afford, hoping to upgrade it later as your needs change, or your credit card balance can accommodate more memory or a bigger hard drive. However, Apple has gone in a different direction, returning to the concept of the original Mac as a closed box computing appliance in the fashion of the iPhone and iPad.