You missed the point in each case we go so far and stop with regards to being our brothers keeper.
I didn't miss the point, rules were literally changed in the cases of smoking and pot that affected how interactions between people happen. In restaurants without smoking you are now no longer going to cause a non-smoker to get lung cancer. In places with legal you are not going to imprison people for doing what everyone does anyhow. This does indeed touch on bettering the public good.
People are allowed and 'get to' die from smoking, drugs, unhealthy food, poisoning the envioerment.... and now we 'Get To' die from covid.
Now you're talking about something completely different from protecting people from harm. In the case of smoking historically, there was risk to oneself, but maybe more importantly to those around the smoker. Now the latter problem has been dealt with to an extent. But if what you're talking about is banning people doing things that you don't like them doing
for their own good, you're talking about something more than being your bother's keeper (i.e. looking out for his well-being); you're talking about making his personal decisions for him. So whether it's smoking, drugs, alcohol, or opening oneself up to infection, you're talking about taking steps to take away the decision from the individual. What I'm still not sure of is why smoking, drugs, the environment, and unhealthy food are in the same category for you as spreading a deadly virus. If someone eats garbage food, they are not infecting me with something that can kill me; although granted, they do indirectly suck up public resources and create problems in other ways that DO affect society. But any lack of personal virtue affects everyone, so if one is to respect free will then there will always be bad decision making that you have to accept from others. That does not have to include spreading disease, or polluting the environment. Those two really don't fit into the same grouping as the others.