They're cheap, easy to re-sell, quick to install, most Jap specialists can tune them with a quick turn around using the same base maps for similar setups..
I think it's very much a case of don't fix what isn't broken. I don't know about you and the VIP generation, but all I need an ECU to do in my car is make the engine turn. The bells and whistles, gauges, 20 sensor inputs and antilags etc. will do sfa for the performance majority of tuned street cars and that is why PFC is still popular. The requirements of most users peaked with this product.