It was a time when folks learned about safety first hand or from family members usually. Youngsters could see the harm it did to an uncle, neighbor, father, brother or sister, and learned what caused the harm.
This is where common sense is learned. One has to make choices, then be able to evaluate them to see if the idea should be repeated, or not. When the person has no experience, there have been no choices, so they never learn what might work, and what won't. Then, years later, we say they have no common sense! Common sense is an opportunity to make choices, good or bad and learn from them.