So, why is affordable dependability a big deal?
The main reason is that pre-made, off-the-shelf components are inevitably going to be used in these embedded systems that people are going to trust. But, many of the components aren't really going to be trustworthy, so something special has to be done to make it all work out.
Two additional, more business-oriented, arguments can be made as well. Undependable systems can be costly. If a system that provides a service breaks (such as an airplane), it can't product income. If it breaks while in use or disrupts plans, people will be unhappy, and you'll lose customers (that's why Wall Street uses fault tolerant computers). Even if things break and you fix them without anyone noticing, it erodes profits.
Now it turns out that we already know how to make very reliable hardware if we have good quality components, but it's just too expensive. Software -- well we are making progress; but we aren't really there yet.