Because they work. Hubby just sent me this Medscape article, which reports the effectiveness of honey when used for cough associated with upper respiratory tract infections in children.
I grew up in a household that embraced many forms of medicine. The only proof of a medicine was in its effectiveness. My father doled out naturopathic pills for common cold and minor fevers, color therapy for sinus infections and breathing problems, homeopathic potions for hair loss and fungal infections. Oh, and fresh ginger juice mixed with warm honey for coughs. Dad was an engineer, not a doctor, but that didn't deter him.
My brother developed kidney stones in his teens. The doctors said these were small enough and would pass. Meanwhile, my poor brother was in horrible pain. I recommended giving him several beers and driving over the pot-holed roads, but nobody listened. After consulting with a local herbalist, dad brought home a pattharchat (literally-lick stone) plant, and fed him a leaf. The next day, he passed two small stones. Problem solved.
Recently, hubby had a bad viral infection. He would get up at night, coughing painfully. We could not use any cough meds that would sedate him because he sees patients at 4 am. We tried the non-sedating cough syrups, hot tea. Nothing worked. Finally at midnight, I grated some fresh ginger, squeezed out a spoonful of juice, added a spoonful of warm honey, and fed it to him.
He slept like a baby.