Nothing is perfect.  That is, everything fails.  With enough data though, failure rates can be measured or estimated, failures follow predictable distributions, and those distributions can be used to estimate the probability of failure and engineer for it.

Resources are finite.  We can always do better, but at some point we have met the needs and have to call it done, at least for the moment.  Resources spent where they are not needed are resources not available later where they are needed.

Life and health are valuable.  Fatalities, injuries, and illnesses have a cost.  While the amounts will always be debated, those values and those costs are not infinite, and must be used to make cost-benefit decisions and to manage finite resources to best improve safety.

Societal expectations set the standards for safety.  Sometimes those expectations are in the form of regulations, sometimes not.  Individuals and organizations are about as safe as society expects.  As time goes by, as life spans increase, society’s expectations will increase.  Individuals and organizations must get safer with time to keep up with or ahead of these expectations.  We cannot judge the past by today’s standards, nor can we judge today by the standards of the past.