Alcohol as a party drug now competes with other party drugs in many markets. Particularly cannabis. This is one reason performance of advertising bans might differ from region to region. Cannabis as a party drug has a pretty broad advertising ban in most places, but alcohol does not. If it's a matter of convincing consumers to buy one party drug instead of the other, an alcohol advertising ban could be highly effective in these particular regions.

>You probably don't go out with friends for a beer more often because you saw an ad for a particular brand of beer.

That's an unjustified assumption. It may very well be the case that "go out with friends for a beer" is such a popular default because it's depicted in advertising and media so often. If your only choice was to drink, then it's easy to see that advertising for alcohol is solely about influencing which alcohol you pick. But that's not the real world, where drinking does compete for attention with other activities.

Alcohol consumption is primarily a cultural phenomena (consumption rates vary GREATLY from country to country. In France people drink 12.2 liters of pure alcohol a year, while in Turkey they drink 2 per year. Neither of these countries are even on either extreme...) Cultures can be changed; history has shown that there is no such thing as an immutable culture. Advertising impacts culture, that is well documented. All of these things we should know. So to suggest that demand for alcohol is immutable seems quite absurd.