Prohibition was the law of the land, even if it was ignored in many cities (notably New York, Detroit, Chicago, Washington DC, Baltimore, etc.) Hollywood production codes prohibited scenes showing people actually drinking, so if the story called for drinking, the best they could do was picture a bottle, or show someone pouring a drink, or people holding glasses.
But according to Daniel Okrent in LAST CALL, a scholarly survey of films in 1929 showed that drinking was evident in 2/3 of them, often favorably. “In AFTER MIDNIGHT, a shy and virginal Norma Shearer takes her very first drink and burst into bloom. Joan Crawford became a star by hoofing on a speakeasy tabletop in OUR DANCING DAUGHTERS.” For the millions of people going to the movie theater each week, scenes of beautiful women and debonair men drinking alcohol looked pretty glamorous. The message served only to further undermine the Prohibition laws.
Drinking was too commonplace to ignore in the movies. I make sure to get that point across in my series.