The problem is that it is a price to pay. When efficiency, savings, and profits is the imperative, the cost savings is "worth" the billion-dollar disaster... right up until it happens.
Very, very few bridges have redundant support structures. Also the 737 MAX is a case of how redundancy DOESN'T always solve issues
The crashes were a result of a single sensor being a point of failure. The update uses two sensors and they must agree with one another.