I have read that the longer chamberings were, originally at least, at the request of pigeon shooters who had come to the understanding of how setback on ignition damaged shot, and patterns. They surmised that more cushion wads between the powder and the shot would help this, thus more space was necessary in the hull.
If that is true it is interesting that the gun and ammunition makers were that hospitable to the requests of customers. But, we have to remember that shooting sports were a much larger component of the average American's interest than today. Results of matches were reported, and followed, with as much fervor as today's NFL or Major League events.
SRH
