What are reasons for why insect repellents do not work?

If they aren't from the natural, organic product line, then insecticides aren't used in the case of Organic Gardening. The standard chemical, commercial, conventional, synthetic insecticides may have instant name recognition among gardeners. They may be more available and more economically priced. But they aren't supposed to be used.

One reason lies in their non organic nature. Another lies in the side effects of their use. For example, some non organic insecticides are target sprays in their effects being directed toward a specific pest population. But others aren't.

Still another lies in the strategies that organic gardening emphasizes. For example, organic gardeners turn to mechanical means such as swatting. Or they try cultural means such as improving plant and soil health. Or they attempt biological means such as bringing in natural enemies to turn the pests into food sources. In the way of a common beneficial among organic gardeners, favorite enemy is the ladybug [Coccinellidae]