You have all missed some very germain points:

1.It about optimises the 6.5 bore case capacity wise.

2.It about optimizes what we refer to as the "standard lenght" action. Why put a 6.5x55 in an 06 length action? You can always down load to any pressure/velosity level.

3. Chamber remers, dies, brass, and cases are everywhere in great quantity and quality. They are also about as cheap as you can get.

4.It feeds through most actions about like corn through a goose's butt. Gunsmiths love it.

5. 264 bullets are beautiful and effecient, and are about right for what most of us will ever hunt.