Why do scientist use a classification system for living things?

It is important to have a classification system for organisms so that we can identify them. If we are able to identify organisms than there are less chances of getting into survival problems and so forth. For example if we were lost in the wilderness and ventured to two trees, both bearing some mysterious fruits. If we already know, say, that poisonous trees have a certain of leaves, than we can avoid it and not kill ourselves by eating the poisoned fruits. This is the same with fishes and also classification is helpful for scientists to discover cures in the fields of medicine and so forth, if we are able to identify them and know their properties.