The work crews are hanging out all day every day, whereas you do your grocery shopping once a week maximum, for less than an hour, and everyone wears a mask to reduce the chance of spreading anything.

On the work crew, if one person gets it, basically everyone else on the crew is guaranteed to get it too. In the grocery store, a single visit, especially with proper precautions taken, is unlikely to spread it.

But the grocery store workers are there all the time, and interacting with a wide variety of people. Sure, the chance per person is lower - but overall?

And the spread on a work crew is limited - there's only 6 people there. But that grocery store worker? Can you define super spreading event?