And Apple is the master of optimizing for things other than just speed. As there are battery life, heat, weight, number of parts, number of suppliers. The best GPU isn't necessary the fastest GPU.
It depends on what you want and what you need. A good deal of people don't need the absolute fastest, most cutting edge GPUs, this is true. And some people do want thinner computers vs. faster one. But where you're making a mistake by assuming that a handful of computers can cover everyone, and the lowest common denominator is all that matters in the industry. As long as there is demand for discrete GPUs, someone will be producing them. And at the moment, there is still plenty of demand.
The rest of the industry has changed as well. AMD buying ATI, turning a former independent GPU company into a mere devision of a CPU maker. Intel developing their own graphics, demoting the GPU to just another chip in the chipset surrounding their CPUs. Laptops outselling desktops, users can't swap and chose their GPU anyway.
I guess you can make anything sound unimportant by adding "mere" in front of it. iOS is but a mere division of Apple as a whole. Same for OSX and Macs, which are but a "mere" division as well.
Nvidia makes GPUs and ARM chipsets. Are their CPUs a "mere" division, too?
And yes, laptops are outselling desktops, but there are plenty of options out there that provide for discrete GPUs. The fact you can't replace them is a distraction to the argument at hand, which is the necessity and viability of discrete GPUs.
The graphics card is on its way following the sound card. Professional musicians might still have a dedicated sound card, for everyone else its just some chip on the mainboard they (need to) know nothing about.
The industry tends to mothball bits and pieces when they're no longer needed, or are replace by something better. Standalone soundcards don't offer much more than integrated chips. The same could be said of floppy disks. By the time Apple removed them, they were already on their way towards being replaced by something better.
GPUs? Integrated chips do have their place, but they're not nearly ready to replace discrete GPUs across the board just yet. They're getting better, no doubt about it, and your theory they're on their way out might possibly be true in another 3-5 years. But now? No. It's just wishful thinking on your part.
