Thats true, but the insects seem to know about it, and about us humans.
I still ponder on the the little bug that landed beside me once, while I read a good book out in the garden; then refused to leave, until I pushed it a little. Then the scent it left, which we could notice even minutes after. For me a pleasant smell, but maybe for a plant or its enimies; not.
Gives a clue about scent that the humans have distorted with its perfumes and all kinds of covering up-scents.