Halvey,
You're absolutely right about getting in shape. But, even those in shape will want for certain weight guns. I know some small framed hunters that when in good shape, they are 135 lbs. and can walk/run the feet off of anyone else. But they get arm fatigue carrying a 7.5 lb 12ga Citori all day. O.K., they can do it, they just prefer to find lighter guns. It's not about "need" but more about "want".