Great article from Gabe suarez
In The Land Of The Blind, The One Eyed Man Is King - Or You Don't Know What You Don't Know
All combat systems, from archery to jujitsu, need to be blooded and tested if they are to true fighting systems rather than sports. The farther away from the combat experience a martial system becomes, the more stylized and artificial it becomes. Its advocates will relate how the "founder"did it way back during the war, although their own experience on the matter is based on third or fourth hand knowledge.
The reader may not immediately see a problem with this. After all, not everyone can be a soldier or a cop, or even a street fighter. Moreover, many cops and soldiers never actually get combat experience, even though they may train for it. Those that do get it, many don't really know why they prevailed, and of those that do know, few feel compelled to teach others how to do so.
Something else that happens is that a trainer may have had a number of contacts, but their scope and nature was limited to a particular environment. For example, consider the SWAT shooter that disdains all reactive index shooting because during his time in service, he never shot on the move, point shot, or ever gave his adversaries a chance to shoot first.
The casual reader might say, "Wow...what a gunfighter". The reality however is that although that man may be a fine tactician, and a great marksman, in the SWAT context, his fights reflect only the SWAT and Spec Ops experience. And such experience is not applicable to the CCW lone operator, or unsupported operator.