[sleepybrett]

It may be something as stupid as a wiring harness layout optimization. You can put the headlights controller at the headlights and only run a single set of CAN bus wires (which are probably in that area anyways), haven't played with CAN I assume they are fairly few and fairly thing gauge, through the firewall of the car.

[maxerickson]

CAN is a 2 wire serial bus using differential signaling. So a couple small wires and maybe some shielding.

[aosmith]

It's not about the cost of wire, it's about the cost of software. This is the auto industry version of MCAS. I wish I was joking.