The problem is that there's no overt way to tell whether the "car" (code) you're looking at is someone's experimental go-kart made by lashing a motor to a few boards, or a well tested and security analyzed commercial product, without explicitly doing those processes on your own.
The problem is all the go-kart hobbyists who make moderately popular go-kart designs end up being asked for all sorts of commercial territory requirements.
The people on the consuming end think "reliability is their job!" and try to force all their requirements and obligations onto the go-kart makers, which usually doesn't end well.