Why living organisms be classified?

After humans came into existence a few million years back from Apes, they slowely started using the materials available in the nature and then slowely civilizations came into existence. Since then, man always wondered where he was? what he was? So he started studying his surroundings and as the time passed, man discovered many things and it became necessary to keep all these things in an order. So man started classifying living things by which one can know the relationship between the species, between species and environment and so on.