In the past, security was the result arising from the reactions because of unwanted incidents or events. In many companies and organizations security was limited to uniformed guards, who only reacted when an incident occurred (e.g. theft in a shop).
So it was considered that safety means uniformed individuals whose trivial task, was merely to refer events. 
Over the years and after several "unfortunate" incidents, it became perceived by the most skeptical that security as a service should be active, effective, and rewarding at the same time, in the business operation. So, from being just a subsequent reaction, it was re-constructed on the principle of prevention and control.
Basic background of this new structure is the stable and constant presence or otherwise static security, where not only the guards must be always visible, performing their duty, but also their professionalism and their diligence.