"why is the fact that a bug won't touch it a good thing?
Plants are no different then animals. Their main purpose is to reproduce and pass along their genes. If your question refers to the actual plant, then an insect feeding on a plant will lower it's vigor, possibly even killing it. Not good for reproduction or long life. If you are referring to insects feeding on the actual fruit, fruits in general are sweet to entice animals and birds to eat them so they will go through the digestive tract and be deposited (hopefully) quite a distance from the mother plant. This increases the odds of the specie survival and keeps the gene pool diverse by allowing what is a heavy seed that can't blow in the wind to become mobile. By an insect eating or damaging the fruit this is less likely to happen.