More copper is bad for cars, because it's expensive, and it's heavy, in that order. Fiber isn't cheap to work with. Termination is involved, whereas copper wir

More copper is bad for cars, because it's expensive, and it's heavy, in that order. Fiber isn't cheap to work with. Termination is involved, whereas copper wire is terminated with a crimp that costs on the order of a cent or cents, if not completely automatically then using automated strip and crimp tech. There's also the small issue where you can't supply power over fiber optics, and indeed these power conductors are the heaviest given the currents required at the standard 12-ish volts. There's been a move toward 48V vehicle DC busses but they're not common yet, last I checked.