If there had never been a single unintended acceleration in a toyota vehicle it would not have been through robust engineering but instead through luck. And we need our vehicles to be safe by design, not through happenstance.
I especially appreciate your comment because my childhood best friend (an electrical engineer who designs safety-critical systems) thinks this way. He started out in avionics, and was the lead designer for the avionics system for a commercial airliner that so far has a very good safety record indeed, and then he moved over to the medical device industry. In his work, "zero defects" is the only standard, and fundamental understanding of how a system works, from the level of subatomic physics on up, is his approach to design with no hidden flaws. That approach is not easy, but he thinks that is the appropriate approach when human lives are at stake.
This problem in general is yet another symptom of the immaturity of the software industry as a whole. Most standards are community standards rather than well accepted and extremely well known official standards. And a lot of best practices still come down to judgment. Moreover, best practices and standards vary greatly depending on the nature of the product. Even within a small sub-field like embedded systems the requirements are very different for a car, airliner, or 3D printer.
It's telling that even at a big company like Toyota which is fairly risk averse and is well known for its commitment to quality and safety they are still capable of churning out pretty crappy software that is hugely important. Software dev is still a pretty hard problem overall, we live in an era where there have been lots of successes, but failure is still common and the consequences of failure can sometimes be severe.
I especially appreciate your comment because my childhood best friend (an electrical engineer who designs safety-critical systems) thinks this way. He started out in avionics, and was the lead designer for the avionics system for a commercial airliner that so far has a very good safety record indeed, and then he moved over to the medical device industry. In his work, "zero defects" is the only standard, and fundamental understanding of how a system works, from the level of subatomic physics on up, is his approach to design with no hidden flaws. That approach is not easy, but he thinks that is the appropriate approach when human lives are at stake.