This is one of the many reasons why airlines are one of the safest ways to travel. Redundancies. Developed from countless failures to ensure they never happen again.
It seems pessimistic and overengineered until you consider the cost of even one fatality. Especially if that fatality is you, or a family member.
In most other industries, this approach is frowned upon. We prefer thinking about the potential for success. Potential for failure is acknowledged with a simple nod of the head and forgotten to avoid it contaminating our sunny disposition.
Planning for failure forces us to think through our vulnerabilities. It sensitises us to a potential increase in the resilience and sustainability of our initiatives.
After all, we would like the most positive outcome. In the absence of this, however rare we might believe that to be, we would prefer a result that is still positive, even if the trajectory was less linear than we expected.