I’ve been surrounded all my life by people who can their own produce. Forty years ago I did know one family whose members got botulism from bad canned goods. One family. Forty years ago.
Realize you are probably talking about families that learned how to do it from their grandparents and had generations of experience behind them.
Not newbies who read something on the web about it or has the “Canning for Dummies” book!