How do you explain the presence of 10% alcohol in the NyQuil®? Do you think it's for coloration, shelf life, marketing gimmick, or sleep aid?
Or, give me your own theory.
What? I have no ideas what you are even asking me.
You stated that there was a history of alcohol being used in the medical industry as a sleep aid. This is demonstrably false. Alcohol can be added to products such as cough and cold supresents to help those products that already have a specific purpose function as a relaxing agent. 10% alcohol in cough medicines does not make those two spoonfulls of the medicine a sleep aid.