Give me one example where humanity cured a social ill by everyone independently choosing to abstain, without organizing, starting a movement, or adopting some p

Give me one example where humanity cured a social ill by everyone independently choosing to abstain, without organizing, starting a movement, or adopting some policy or technological solution. Show me one time where mass numbers of people said "i'm quitting smoking cold turkey" at the same time, or show me a country that cured obesity because everyone woke up one day and decided to eat less. You can't.