So what? You think all game creators will jump to optimizing for 16 threads, because that's what AMD offers for high-end gaming desktops? Get real.
Game studios have to earn money by selling copies, not race for the best fps possible on high-end desktops.
Most people will still game on 4 cores - either from Intel or AMD (Ryzen 3/5 will be mainstream, Ryzen 7 is for enthusiasts).
And keep in mind we're still talking about desktops, while most PCs are laptops (also among frequent gamers).
Intel manages to squeeze a 65W i7 down to 45W laptop-sensible version (e.g. 6700 -> 6700HQ).
Ryzen 7 has a nominal TDP of 95W, but it's been shown that it can suck 120W in max load.
This means that - to keep 8 cores - AMD would have to cut power draw by half and that would simply obliterate single-thread performane (already not mind-blowing).
So yes, AMD managed to make an excellent flagship 8C/16T CPU for the Ryzen line.
But in the long run, when market becomes saturated with Ryzen CPUs, it's highly probable that most of them (by far) will be 4 core units.
Above all, a CPU design has to be very flexible to work well in many different tasks, in many different types of PCs.
However, a GPU doesn't have to be flexible. It can concentrate on multi-thread performance above anything else.
Why change this status quo? Why force game studios to spend huge money on optimizing games for the minority of >4C owners, when it really doesn't affect the image quality nor FPS?
Sure, if you're very brave, you can blame all the game studios that they don't utilize more cores than 99% of their clients have.
But we have (at least) equally good reasons to blame AMD for not making a CPU that matches the current state gaming market.
You do realize Intel measures TDP at base clock, right? Also, that laptop version of 6700 has very little to do with the desktop version. It has been this way for years. Also, 16 threads laptop CPU. Haven't seen that one yet have we?