That actually makes sense. FPGAs are very complex to program, even though the gap between software and hardware programming has been narrowed with High Level Synthesis (e.g. OpenCL). I can see how it is just easier to use a GPU that is simpler to program, or a TPU that already has compatible libraries built for that abstract the low level details.

However, FPGAs have been increasing in area and available resources in recent years. It is still not enough circuitry?