It is presumptuous to believe that all the fancy breeding that is done to enhance the characteristics of flowers necessarily ‘improves’ them. Breeding only makes flowers more appealing to those who enjoy them in their gardens. Most flowers were already quite efficient for their intended function in their respective natural habitats long before humans started tampering with them. As far as flowers are concerned, they only need to get pollinated.
Some flowers use flashy color or patterns to be visually attractive to pollinators. Others use fragrance to be olfactorily appealing. Small but profuse flowers that are neither colorful nor fragrant have given up on insect or animal pollinators, so instead rely on the wind to disperse their pollen.
Not many flowers are both remarkably colorful and remarkably fragrant like freesia, lilac and wisteria were earlier in spring. Lily and bearded iris are of course very colorful, but not all types are fragrant. The big and bold flowers of cereus cactus, moon flower and angel’s trumpet are only fragrant because they bloom at night, and rely on nocturnal pollinators who benefit from a bit more guidance in the dark.
Many fragrant flowers are somewhat showy, like gardenia, star jasmine, pink jasmine and honeysuckle. (However, gardenia are almost never healthy and showy locally.) Many of the most reliably fragrant flowers are really not much to brag about. Pittosporum tobira, Pittosporum undulatum and sweet osmanthus are known more for the appealing evergreen foliage than for their small and nondescript flowers. The flowers of sweet osmanthus may actually be difficult to find amongst the obscuring foliage. Night blooming jasmine is sometimes planted around corners or in the background because even the foliage is not too appealing, although the powerful candy-like fragrance is a favorite for warm evenings.
Fragrant flowers can be annuals like sweet alyssum, bulbs like hyacinth, or perennials like tuberose. Woody plants with fragrant flowers can be vines like stephanotis, shrubs like mock orange (Philadelphus spp.), or trees like Southern magnolia. Some have brief bloom seasons, while others bloom for quite a while.