Clean plates are required for each trip to a buffet because:

Clean plates are required for each trip to a buffet primarily to prevent contamination. When guests use the same plate multiple times, there is a risk of transferring bacteria or pathogens from previously served food to new items. This cross-contamination can lead to foodborne illnesses, which are a significant concern in any setting that serves food.

By providing clean plates for each trip, the establishment minimizes the chances of food contamination. It's crucial to maintain a hygienic environment, particularly at buffets where the food is often left out and exposed to various environmental factors. Using a fresh plate each time also encourages guests to serve themselves without the risk of mixing different food types, which can further enhance food safety practices.