Your example thus kind of shows the opposite: dangerous things can be made safe, with a solid understanding of their risks and techniques that are proven to make them safe. We have neither the former nor the the latter for social media.
Like I said in another comment - if a parent is working 3 jobs and doesn't have time for their children, change the subsidies given to the parent for having children. Make child care free or really accessible.
A child needs a parent or at least a role model. If you ban social media, the children will still see random crap on the internet, whether it's YouTube videos or content from random sites too small or shady to be regulated. Do you want 100% of the internet regulated or do you want the government to empower the children and their parents? We have the resources, we just haven't allocated them correctly. Otherwise a parent would have time to spend with their children.
And the people using asbestos in their homes, or buying homes with asbestos, are endangering themselves. How likely is that an improperly installed or maintained asbestos is going to affect a whole neighborhood?
Similar to how if you're using a insecure program written in C, whoever finds the bug should tell you immediately - don't use that program.
[0] You might say that asbestos from 1 house would affect the whole neighborhood but that would be similar to how a smoker smoking in the streets would affect the neighborhood. Second-hand smoking and second-hand asbestos are bad but they're negligible compared to living with a smoker who smokes indoors with the windows closed or smoking yourself.