Normally, with say influenza, the public takes responsibility for vaccinations, seeking diagnosis, treatment, self-distancing and isolation. When there is a dangerous infectious disease like COVID-19, because the public is unable to recognise infected people and avoid dangerous contact, they expect to be protected, with infected people separated and treated. Voluntary control is displaced by public authority.

When a large part of the population is not very vulnerable, for example only 8% of worldwide COVID-19 deaths to March 30th were people aged under 60 years, the social and economic costs from restrictions to young people’s education and careers should be weighed against the small probability of significant health benefits when restrictions are being considered for renewal. If under 60s act as vectors in transmitting the disease to the vulnerable 92% of over 60s, the latter might not regard their own voluntary social distancing and self-isolation as sufficient to protect them. The calculation of what age groups to compulsorily restrict would require more transmission data than I have available. Authorities have usually imposed the same restrictions whatever are peoples’ ages.

http://www.martinknox.wordpress.com