Right, but the entire concept hinges on the fact that the ones with immunity therefore provide protection to the minority of the population that does not have it, by mitigating transmission. Achieving herd immunity in a human society raises the very question: how do you do so while *effectively* protecting the people who will inevitably end up as part of the percentage of the population who can't afford to acquire immunity through the virus itself? Even if we all agree that more extreme measures, like stay at home orders, are reasonable for retirement communities and nursing homes, how do we account for this:
Tons of vulnerable/at-risk people who can't isolate from non-vulnerable people due to a wide variety of circumstances (cultural, financial, housing density, previously unidentified underlying conditions, etc.) would basically be told to take their lives in their own hands and hope for the best because society will consider them expendable. How do we tell America "many of you will die avoidable deaths" in favor of saving costs? Bullying aside, that is what would happen, is it not?
And that's all *if* immunity to COVID-19 works the way we hope it does.