In answer to the posted question, because they met the needs and expectations of most 1935-1955+/- shooters. And the March to Magnums of the '50s-60's made hands hurt, so they enlarged the grips.

Oversimplified? Probably, but close. Plus, Magnas fit a lot of hands, witness this thread. They sure fit mine. Though I love the look of targets on 5"-6" barrels and up.

Long live variety!.

Regards,

Dyson