Why is it important that food servers are trained to know food ingredients?

It is important to know the ingredients because you are able to know nutritional facts about the food which this is helpful when dealing with a Diabetic and you are able to prevent someone from eating a substance they are allergic to.

This answer isn't textbook but it's what I was told

Iwould say being around others who are not drug free is the wrong step because your peers are likely to influence any new or past habits