They could if there are human pickers.

In any event, delivery doesn't always mean the worst of the produce aisle, and while I noted that the incentive of tips might not transfer to robots, keeping repeat customers might be enough incentive for a way to be found to not make robots and grocery synonymous with only frozen food. That might mean human pickers; better automation on the food selection system; pre-inspected, washed and packaged fruits & veggies; etc.