Why do perfumes smell?

The sense of smell is intended to help people to distinguish between things that will prove to be useful, and things that are dangerous. Flowers are associated with edible fruits and vegetables, so the perfume of a flower is an indication of valuable plant life. And since flowers are part of an evolutionary strategy that involves attracting animals to the plant to help that plant to spread its pollen and/or seeds, flowers evolve to take advantage of the sense of smell. Evolution is therefore working from two directions, both the evolution of plants and that of people, to produce this phenomenon, that flowers smell good. People who manufacture perfume, then, make use of the existence of good smelling flowers to create a product which people can use to make themselves smell better. Perfumes do use some other substances besides nectar from flowers, but flowers are the primary source of perfume.