I expect, and one of the lawyers reading can probably clarify, that Tesla's liability and risk changes if you're using the car for a commercial venture with their blessing. This specifically says you can't do that, so you're in violation of the terms of service and presumably that is enough to shield them.
If Tesla isn't confident enough in their self-driving service to accept the liability then I doubt it's good enough to be approved for road-use anyway. It sounds like they're trying to set a precedent to kill competition before it starts. Hopefully other self-driving car manufacturers force their hand or kill their business.
Perhaps, but it is not uncommon for example for chip manufacturers to specifically say their parts cannot be used in safety systems without their express written authorization. They are certainly confident their chips work, and they sell them by the bucket full, but if someone dies as a result of using their product that their chips are in, they don't want to be liable. They use those disclaimers to shift liability to the person who designed it in.
There is a funny example of such a disclaimer in the Java license agreement, it says:
"You acknowledge that Software is not designed, licensed or intended for use in the design, construction, operation or maintenance of any nuclear facility"
