I understand that the Zouave uniform was not a major uniform to begin with, but why did the style leave the US military completely after the war? Why, with the different service uniforms that existed during and after the period, did this colorful style leave by the start of the 20th century.
One of the major reasons was changing fashion trends in the worlds militaries. After Napoleon's wars, French inspired military dress was very popular. Kepis, epaulletts, sashes and Zouaves style uniforms to name a few. They did this to imitate the French military since it was seen as the land military power of the world. After the French loss in the Franco- Prussian war in 1871, the fashion trend changed toward Prussian style. The US military adopted the Pickelhaube, but for mostly cerimonial or formal use. But logically the practicality of uniformity made manufacturing easier, allowing more troops to be clothed more efficently and completely.