You obviously have not done 3D animations, ray tracing, major video editing, or heavy duty simulation science. Those are the thing that use 18 or even more cores in a workstation grade computer, sometimes in realtime. I was looking at Intels Xeon processor page and their new Platinum line starts with 20 cores. Some had 60. I saw one that was priced over $60,000 for a single processor chip! Yes, there is software that will use those cores and they do produce lots of heat!
Great.
So again, how many of these does Apple believe they're going to sell? Seems to be a rather niche market. (I used to work for a large world renowned advertising agency in Chicago that did video pre and post editing, btw. We had maybe a handful of high end video processing systems because of their cost.)
My secondary point was that anyone (meaning any average/home user) who purchases one of these likely has more money than brains. My compute requirements do include audio & video editing & compilation, virtualization and other fairly cpu, memory and disk intensive tasks. Still, I hardly touch the 8 cores (16 threads) in my pc today. Then again it's highly unlikely I'm using software intended to take advantage of those cores and threads.
I should've qualified my statements a whole lot better than I did....