Yet even though scientists knew where that smell was coming from, they didn't know the answer to another basic question: why make it? A team of British, Hungarian, and Swedish scientists investigated this question recently, publishing their findings this month in Nature Microbiology.
— Scientific American looks at why bacteria in dirt bother to create the geosmin that makes it smell good. Read more in Dirt Doesn't Smell Like Dirt.
Fascinating! Should have known, the energy cost to make odor molecules is too high for those molecule not to be functional.