Everyone has given good explanations.

DH and I wondered how we'd manage if, when older, we had to go to a different place for each of our food groups every couple of days. We visited the ancient market in Palermo with our "adopted" taxi driver and he suggested that the super mercato is slowly replacing it. Although the SM's we did visit in Italy had areas where the farmers' trucks were backed up so I'm hoping that the freshness issue is still vital.