Some mitigating factors:
- they can do slow releases. So if a serious anomaly does occur it is unlikely to be with your car.
- the conditons of space make errors much more catosptrophic. Although I can imagine similarly catosptrophic scenarios with a car, there are also more opportunities to safely rectify the situation (like the car pulling over and refusing to drive if things are not ok). In space, the satellite cannot just stop and wait for a tow truck to arrive.
- there is only one satellite to test the update on. If they screw it up, it's gone. With cars, there are many to test on, so errors will turn up and be fixed faster.
But back to the issue of risk:
Just like with drunk driving, you are at risk of somebody else's car going haywire as well, so it's a risk regardless of whether you yourself updated or not. At that point, the difference between your existing risk and the risk you take on from the update is probably not that great, so might as well just do the update.
Also every technological advancement we are reducing fatality. We are not bringing it to complete zero but we are definitely reducing it.
I think it's a tradeoff. If self-driving cars can save tens of thousands of lives in the US every year, how many should we be willing to risk to enable this?
Eventually your insurance company may force this on you due to higher premiums, or government may make injuring someone in a manual car accident a crime like assault.
Tesla is the only offender I know about when it comes to real cars that actually exist and have obnoxious over-the-air update systems, because normal car companies are constrained by their contracts with dealer networks, so any software updates they might want to push on us would have to be done through the normal vehicle service program. This can easily be avoided by choosing a different mechanic. One can't very well choose a different mechanic if you are stuck a Tesla-like system that pushes diffs at you via radio, and that's what concerns me.