Indeed. Who’s to say that viruses might not lose their ability to infect humans if humans don’t carry them for the next 10-15 years?

If everyone strictly followed the teachings of Christ and all humans were monogamous for an entire generation, would we lose herd immunity to STDs or would STDs go extinct?

Well the argument is masks work better until there’s a mask shortage for any reason, or any large drop in percentage of people wearing a mask. Then you might see an impactfully large pandemic that could have been avoided if we had more frequent sub clinical or non epidemic infections over the preceeding decades.

For example if there were a war and China cut off EU/USA supply for N95’s. In the 1-6 months it might take USA to build domestic capacity there could be a large outbreak of something which cripples our national readiness at a critical time.