We've basically split our population into two groups, a large group that is (hopefully) staying put and not interacting with the world as much as possible, and

We've basically split our population into two groups, a large group that is (hopefully) staying put and not interacting with the world as much as possible, and a small group that is still going about business as usual, because we need them to. The smaller group is hopefully doing everything they can reduce their risks, but small risks repeated frequently become likely odds. As a civilization, this still buys us a lot (in the US, it's the difference between 30 million and 230 million people catching the disease and some percent of them dying), but even if you assume all 3 million grocery store employees are in the low-risk 20-29 demographic, we're still expecting ~1200 of them to die from COVID-19, given our current understanding of the disease. That alone would make working in a grocery store roughly as dangerous as being a coal miner in the present day US, or roughly 4 times more dangerous than being a police officer; it gets worse if you assume many employees are not in the lowest risk category.