If you want to build a safe system, you must understand how perception affects practice.
People tend to work to prove the things they want to be true.
If a system is perceived to be unsafe, then people may be motivated to do the work needed to make it safe, to disprove perception.
But once it's perceived to be safe, they may neglect that work, because they no longer feel the need to defend their belief.
Complacency is the enemy when safety depends on labor.