Pistols, such as those you showed, were first put in use by men on horseback. The appeal was obviously the revolving chamber which allowed for quicker shooting. Since these men would be on horseback, often fighting the quick drawing (bow and arrow and single shot rifle) Comanches in Texas, they were not designed for quick draw duels. Colt's revolving chamber pistols were initially disregarded. It was the Texas Rangers that brought the Colt into the mainstream. Many rangers fought with Taylor's army in the Mexican American war. American soldiers were awed by the Rangers fighting prowess, their ability to fight while mounted, and their unique firearms. From that point on the Colt revolver picked up steam and eventually made pistols for the military. I suppose the overall point is that these guns were not developed for duels but for horseback, quick fire, fighting. Cowboys that carried them did so more for the rapidity of the revolving chamber than for the quickness of the draw. Furthermore, those outlaws that may have been interested in a shorter barrel hadn't the clout to have Colt redesign the pistol.

Work Cited:

S.C. Gwynne, Empire of the Summer Moon: Quanah Parker and the Rise and Fall of the Comanches, the Most Powerful Indian Tribe in American History (New York: Scribner, 2010), ebook.