Yes if a partner dies when the family rely on their income, there will be a major impact on the finances of the household. And yes, life insurance would solve at least that impact.
BUT not everyone can get life insurance that covers everything. A LOT of people are born as children with illnesses that can have an impact on life expectancy, and so these will often not be covered by life insurance. With some conditions, it may be that you can not get any life insurance. Or the costs may be too high.
And when I was young and took out life insurance policies routinely excluded causes of death such as suicide or risky behaviour.
But easier to just blame the individuals.