Also Mathews does not offer adjustable cams mainly because peak performance is affected by adjustments ( backing a 30" down to 28" would not perform as well as a cam designed specifically for 28" draw) !
That would be my comment as well. By offering a different cam for each inch or half of draw length Mathews can optimize the force draw curve for each draw length thus giving the "best" storage and release of energy for any given draw length.