Specialized coprocessors are super common but they're basically all ASICs with nary an FPGA to be found. In theory you could have reconfigurable co-processors on a mainstream chip but nobody does that - partially because the latency involved in reconfiguring the FPGA makes it a losing proposition in most cases.

There are uses for FPGAs where there's enough money at stake for the hardware development but the number of units is small - stuff like high frequency trading or many defense roles. Or in the development of new hardware. But it's pretty niche.

How is every consumer device with a display "niche"?

Dedicated GPUs were not required historically to drive displays, and this was done by the CPU instead.

Similarly, we’re finding more functions we can take away from the CPU and migrate to dedicated circuitry (FPGAs) that can handle those tasks more efficiently than the CPU can.

dedicated circuitry != FPGAs.

GPU's avoid the overhead of FPGAs while still retaining a lot of flexibility.

Because they were all 2D. And the idea that GPUs would be used for mobile computing was not obvious.

Maybe 25 years ago. 10 years ago they were commonplace. Intel shipped integrated 3d graphics by no later than 1999:

https://en.wikipedia.org/wiki/Intel_810

Lol I don't know who bought that. Anyone who wanted 3D was buying Voodoo, RIVA TNT or ATI RAGE. Everyone else was happily 2D and running Word 95.

But, to clarify, I was speaking of consumer/mobile. The original iPhone was quite revolutionary for having a decent PowerVR graphics chip. High end symbian phones just had a CPU. See for example https://en.wikipedia.org/wiki/Nokia_6110_Navigator or https://en.wikipedia.org/wiki/Motorola_Razr2

Even though GPGPU was already big in 2008, people still thought of it as a difficult to use coprocessor for big compute jobs. Much as people consider FPGAs now.

I didn't highlight it as a desirable 3d processor, I pointed it out because 3d was essentially becoming default at that point.

And the first iPhone shipping with a powerful graphics chip is a counter to your argument that the future of mobile wasn't clear. The people with the ideas wanted a graphics processor.

The fact that the entire industry apart from Apple (a computer company, not a phone/device company) were completely ignoring 3D exactly shows that it was NOT obvious or clear. After Apple demonstrated the potential it became clear.

Okay, I should have clarify the 'niche' thing 10 years ago was not GPU per se, but of course GPGPU, the GPU as a specialized coprocessor for general purpose computation, not restricted to graphics processing and output.