Sam the issue is not just about how humans get natural immunity.
Reality is many do get sick. And it was overwhelming the health care system.
Too many getting sick at the same time. Needing O2. Intubation etc. Couldnt cope.
Even if the vast majority did get mild disease the "so called small number" of cases that needed hospitalization was just too many.
At least that's what Italy and China told us.
When there is too much rain it overwhelms the drainage system.
When there is drought the reservoirs run out of water.
When there are too many cars the transport system ends up in gridlock.
When there is a massive power failure there are insufficient linesmen to fix the grid and people go for days or weeks without power.
And when there are too many sick people the healthcare system is overwhelmed.
That is just part and parcel of life. Shit happens and we have to deal with it.