Does Beer still move by rail? The beer cars made me think of this.
Those beer cars were for shipping barrels of beer. Prior to prohibition, over 80% of beer in the US was sold on draught at taverns. Even industry giants like Pabst, Schlitz, Ballantine, and Anheuser-Busch had just one big brewery. They had to ship those barrels all over the nation.
After Prohibition, draught beer consumption began to decline as the major brewers improved their bottling and then canning processes. Packaged beer is pasteurized and doesn't require refrigerated railcars.
Also after WWII, I know that our local brewery, Anheuser-Busch, brought the mountain to Mohammed: they opened breweries in Newark, NJ and Los Angeles, CA. So between the local breweries and better packaging, the beer cars became unnecessary.