Because the Berns-Martin split-front holsters can only be used with revolvers (the rear loop of the trigger guard being engaged to grasp the revolver), and the near universal adoption of semi-automatic pistols by American law enforcement in the 1980s, the split-front revolver holster has fallen out of favor with American police forces since the 1980s.
As a result of the widespread adoption of semi-automatic pistols by American law enforcement agencies in the 1980s, and the limitations of Berns-Martin split-front holsters to revolvers only, these holsters have become less popular among American police forces since the 1980s.