Honestly, the weight of a rifle would be very hard to regulate, and controversial. When I say controversial, who decides the weight of said rifle? Will it be 13.5, 15, or 17-lbs? Will that be with or without scope? With or without loaded magazine? With or without suppressor? Who would make that discission? What happens if PRS chooses 15-lbs, and the NRL chooses 18-lbs? Then you're forcing people to choose sides so to speak.
Then there's the people like me, who already have several rifle builds. All built to be similar in ergonomics, and my preference on how it balances in my hands. Common barrel contours, same stocks, actions, scope etc. I never considered weight as a primary factor, even though my rifles would be considered heavy by some. I'm in good shape, live at 8200-ft in elevation, and would have no problems hauling one of my match rifles with me in a hunting senerio. Hell, I haul them, plus a heavy pack loaded with ammo in field style matches like what Competition Dynamics puts on, walking, jogging, running several miles.
Never weighed my rifles but assume they are in the 17 to 18-lbs range with scope. So, someone decides match rifles over 16-lbs are not allowed. Myself and hundreds others now need to rebarrel, or some how reduce the weight, or purchase another match rifle to meet the rule. I can tell you, that would go over like a lead balloon.