I think the stores are critical infrastructure for food but that individual staff issues is not so critical, and more on the lines of essential. However, enoug

I think the stores are critical infrastructure for food but that individual staff issues is not so critical, and more on the lines of essential. However, enough grocery stores have to be kept running, or else people could run out of food, or the food supply chain could be disrupted. So, "essential workers" means that they have to be protected and encouraged to work as a group, but that if some individual ones quit or have to take time off work, it will be OK. Whereas in this crisis, if even one grocery store closed, that could, depending on the area, cause a problem.