The settings of the both the short and the feature films also look a lot like real life locations, such as a business office or a dance studio. People are often looking for work in these tales. Both the everyday nature of the characters and the job hunting reflects the Depression. All of these films avoid the desperate real life poverty that afflicted Americans in this era. Once the singing and dancing starts, both the shorts and the features travel at once into a world of escapism.
Realism vanishes into the background, while elaborate musical production numbers occur.
These can be elaborately costumed, with substantial production values. Like Busby Berkeley, Mack often has a troupe of chorus girls who back up the leads. The Desert Song has extraordinarily beautiful melodies, and an appealing story, so it is not surprising that it has been filmed so often. I believe that at one time it was also a favorite of high school students doing a class play. Warner Brothers was always the most liberal of the Hollywood studios, and it is not surprising that they would end up with the film rights.