They have to be. And the others writing this stuff likely do not deal with real systems with thousands of customers, a team who needs to get paid, and a reputation to uphold. Fatal errors that cause permanent damage to a business are unacceptable.

Designing reliable, stable, and correct systems is already a high level task. When you actually need to write the code for it, it's not a lot and you should write it with precision. When creating novel or differently complex systems, you should (or need to) be doing it yourself anyway.