Final nail in the coffin...
America doesn't need subcompacts anymore. The cost to upgrade to a compact is not much more, and you get a bigger car for practicality. Fuel prices are becoming more affordable as motors are being more fuel efficient, and as well, the industry is slowly leaning toward EV.
In an enthusiast POV, the FiST is still not in high demand. It's a fun car, but the ceiling is limited in real performance, the car is narrow, high COG, wheels rub at 225's, no LSD, etc. People looking for a hot hatch or entry level performance car would easily rather get a FoST, GTI, Si, etc. Something bigger and more practical, and more power out the door, because not every enthusiast is a hardcore tuner that wants to void warranty 800 miles in.
It's too bad, the FiST is an underrated car and it's a blast to drive, but it's too excessive for the average consumer. And it's not quite "good" enough to be taken for a serious performance car which is why a lot of people drive it for a few years and then move on to something with more potential. So... the FiST is sort of left in the middle of no where.