Because car industry regulations haven't caught up with cars being software on wheels yet. Most regulations in general haven't caught up with software eating the world and the "move fast and break things" mentality. This is not just an arguably bad mentality, but when human lives are at stake, it's a very dangerous one as well.

Besides, companies the size and influence of Tesla can lobby their way out of regulations. With Musk now becoming more politically involved, it's doubtful we'll see any of this change in the next 4 years at least.