CAN bus wiring has a big effect on how fast data can go on CAN. CAN bits are normally 2000ns (2 microseconds, or 500kbit/sec) or longer for slower buses (a J1939 CAN bus runs at 250kbit/sec and can be up to 40m long). But CAN FD has the promise of much faster speeds on conventional CAN bus wiring, up to 8Mbit/sec (i.e. 125ns bit times). Yet most of the automotive industry is using CAN FD at just 2Mbit/sec or even slower. Why is this?