Prohibition works very well - it just has externalized costs.

Excessive drinking was curtailed by 70% during the alcohol prohibition era, and acute drinking was a problem (it was more concentrated).

There is zero doubt how much healthier at least some people would have been.

The price paid was limiting freedom for many, and some increase in crime.

Allowing children to smoke and drink from age 12 would be a social disaster, it's not even an argument - obviously - the 'prohibition' works - and in that case, there's nary any negative externality.

Yes, there is 'lost economic potential' from not having kids buy smokes, there is a degree of authoritarianism, but those are trade-offs we are happy to make.

The question is the degree of restrictions on basic freedom, and the direct / indirect externalizations - aka 'underground pubs', 'black market', 'lost benefits' etc.

For social media - kids 'sneaking' onto regular social media is hardly an enormous hazard.

There are also 'critical mass' problems - for example, its' very hard to get people away from a system if they will 'feel left out'.

The negative externalizations of a teen social media ban are likely most related to the positive aspects of social media aka community, connection etc outside of school.

Twitch, for example, I think is fine for kids.

There is probably a happy medium that's a bit nicer, for example, banning phones in schools is something that everyone seems to be ok with - that sets a good baseline.

We may want other social media places for 12-18 to have parental opt-ins and to be a bit more assertive around harassment and bullying - which is a very serious thing, and very pernicious as well. It's really hard to monitor.

Creating 'PG spaces' is probably what most parents want.

The worst negative externalization from all of this is probably state-implemented age verification, identity issues, and the leaks, failures and excessive authoritarianism that can come about aka 'slippery slope', which is a serious argument. Even then - there are smart ways to do this which avoid many of those risks.

>Allowing children to smoke and drink from age 12 would be a social disaster, it's not even an argument - obviously - the 'prohibition' works - and in that case, there's nary any negative externality.

The negative externality is the huge amount of young adults damaging their bodies with excessive alcohol consumption in college because they never learned to drink healthily. The US with its late legal age for alcohol has a far bigger problem with youth alcohol abuse than European countries where youth are introduced to alcohol earlier.