Because if sunlight really sterilized the air, which is transparent, it surely would disinfect every surface it touches. In reality, sunlight does disinfect, bu

Because if sunlight really sterilized the air, which is transparent, it surely would disinfect every surface it touches. In reality, sunlight does disinfect, but life has evolved to withstand it enough to find a safe environment. BTW, hospital UV sterilizers work better because they're more intense than sunlight's UV.