This interesting to think about, but truth is a lot of at-risk people still need to be out there. Take all the workers for critical infrastructure, businesses,

This interesting to think about, but truth is a lot of at-risk people still need to be out there. Take all the workers for critical infrastructure, businesses, hospitals, etc. They need "the outside" to be as clean as possible too. Consider an emergency, where someone who wants to shelter needs to go somewhere (say, the hospital, airport, etc), or receive someone at their house (say a doctor, technician, etc). Or consider groceries and other needs that come from the outside but are brought to people sheltering. You want "the outside" to be as clean as possible in those cases too. Perfect isolation from the outside world isn't possible, but with a general shelter-in-place, there's fewer chances that "the outside" is virulent. Very similar to herd-immunity and vaccines.