Yes, because if you're a hardcore liver-failure-in-three-years alcoholic, quitting cold turkey will kill you, and if you're in the hospital for some other issue, they will make sure you get some alcohol.

Doctors don't prescribe it to people who aren't already putting away 50 drinks a week.

I like your point that doctors prescribe things that are necessary to patients, alcohol is one of those things, and there are clear and well-understood examples of when it is medically necessary for a doctor to prescribe and administer alcohol to a patient.