The problem with any tech is that it's nearly impossible to make it perfect. In some situations like airbags, you can make the system very simple and independent, so it's not prone to failure.
Airbags aren't perfect. I know that for sure as i blew the side impact bag in a VW when a tyre popped. How do you think the car knows whether to deploy an airbag? A lateral g sensor, or in more advanced systems there may be sensors in the doors/pillars. Its still electronics that can go wrong.