Average consumers obviously don't own desktops. This has been true for many years already. Desktop is a niche. So we can assume that desktop owners don't behave like average consumers.
My experience about desktops (both gamedev workstations and home gaming PCs) is that people only upgrade GPU and HDD/SDD (add another HDD/SSD when space runs out). If you want to change anything else, then you buy a new computer. Sometimes I have seen people upgrade memory, if they have skimped on memory when they bought their computer. Gamedev companies behave exactly like this too. Workstations get bought without GPU and GPUs get replaced eventually, if there's a need for that before it's time to buy a new computer.
There are still some instances where companies buy cheap desktops instead of laptops. Some companies are still old fashioned and don't like the possibility that their employees can take a computer with them outside the office. Most companies nowadays of course feel the exact opposite (extra hours = good). For these kinds of desktops integrated CPU+GPU+memory solutions are preferable. Nobody is ever going to update any computer like this. But the existing Intel GPUs (24 EU GT2 models) are more than fine for this purpose. No need for a fat integrated Radeon. And this is a market that is getting smaller and smaller. Laptops are the workhorses of modern companies. Except gamedev and HPC of course.
