[yareal]

Because it was a defining reason for their creation. Uniforms in policing represented a change in public thinking about crime prevention vs crime reaction. It marked the moment in time when the modern police force was effectively born.

Before that, we did have police, but they were different in meaningful ways. Such forces were largely concerned with dealing with crime post facto, and were not always considered particularly professional. The uniforms were a fundamental shift in the theory of policing.