I know that around 1950 Columbia started re-releasing shorts from the 1930s and 1940s so as to increase their circulation right about the time they more or less cut the shorts department down to nothing except the Stooges and Andy Clyde. Typically with shorts, a theater would purchase the rights to show a given short and be sent a copy to use. With your major shorts stars, like The Three Stooges, Leon Errol, etc., having those shorts on the night's card could be the difference in a good night and a bad one.
To answer the question, profits for shorts really depended on the theaters purchasing the rights to show it. What happened over time was that the run time of the features grew to be so long that it became too burdensome on the crowd to show a short or two before the feature. There were just a handful of series that were popular enough to make it worthwhile for studios like Columbia to keep churning out their most popular stars.