Alcohol IS a drug. But, to be fair, under that criteria, so is sugar etc – thing is, everything we ingest into our body has chemical components and can be considered a drug.
Alcohol is a proven depressant though – and this may be the crux of the question. It leaves people more depressed than they were before imbibing. And THIS is the thing that hurts to many – people use alcohol to “self-medicate” and it may even help for a few hours. But those few hours? Lead to many, many more on the negative side.
It’s a hard pattern to drop. But – someone depressed and self-medicating with alcohol is fighting a losing battle.