Hey, can't speak for Apple, but I'll try. You have to look at the cost/value for each and every component in a computer. The value of Thunderbolt 3, to 99.999% of users is zero! If you need a desktop class GPU, then you need a Mac Pro. But in your case, since you need specifically Nvidia, you can choose a Hackintosh or a Windows machine.
It's the same reason they didn't include USB C or DDR 4. It would increase costs for literally no gain in terms of market share. These also might have slowed delivery of the new machines as both USB C and DDR 4 require new tooling to their cases.
You (and others) might think Apple is wrong in their thinking, but I don't. I think they got it just right with this release.
And before anyone complains about the price, the value on the 27 iMac is INCREDIBLE. A 27" 5k monitor ALONE is upwards of 2K -- and don't even have the color range of the new iMac models. The flash storage is faster than any SSD, and the keyboards and trackpads are fantastic. I could go on.
Yes, getting a spinning disk is not the right choice for the iMac, but the value of the computer is literally unbeatable.
So, in sum, the new iMac is fantastic for many, many of us. But if you need NVidia, don't wait for the right Mac. Get a high end Windows 10 workstation that has the hardware you need to do the work you have to do. If you get a 4K monitor and a desktop computer, you'll save some money as well.
Anyone know why the new iMac doesn't include Thunderbolt 3? It is necessary for me to continue to hold off purchasing any new computers until they have Thunderbolt 3 (I need to be able to use external Nvidia GPU for ray tracing with Cuda cores).
Intel announced Thunderbolt 3 months ago. In the past, Apple has been ahead of the curve with Thunderbolt. It's really surprising to me that they are releasing a new Mac without it.