While it may be true that margins are independent of the buyer at a given scale, margins certainly do depend on scale. If 15% of the population is buying 75% of the alcohol (these are not ridiculous numbers), cutting that 15% out would put many alcohol producers (in particular those who sell cheap) out of business.
I don’t think it would put them out of business. Rather they would have to increase costs to stay in business.
Essentially a disturbing way to look at it is that the people with alcohol addiction are allowing everyone else to be able to consume alcohol for cheaper than it would otherwise be.
Same phenomena exist for other addictive things like sugar in soda and free to play video games. (Although obviously soda and video games are nowhere close to alcohol in terms of destructive potential for those who develop an addiction).
