The springs are hardly the reason race bindings weigh more; race bindings utilize metal housings, which make a much greater difference in weight than just heavier springs. Metal is more durable than plastic, especially when the forces of higher DIN settings are exerting outward.
There is no functional advantage to having lightweight bindings on a race course. Heavy is good, the mass absorbs the energy of impact with irregularities in the snow, smoothing the ride, and allowing the ski to track better. . Lightweight bindings have always been a compromise to lower material costs so they will be more affordable for the recreational skier (metal is more expensive than plastic), and to appease wimpy recreational skiers who don't have the strength to carry quality gear without becoming whiny.
True for the most part VA. However, it can also be dependent on the event. For Slalom I like the ski to be a bit lighter. I actually ended up changing out PX18s for PX15s on my dynastars and there was quite a difference. IIRC the PX15 Race was 52 ounces/binding v. 64 oz for the PX18 Race and I could actually feel the difference. (I noticed originally because my training pair had a PX 14 and when i jumped from one pair to the other it was obvious). I know quite a few others who stick with the PX15 on a Rossi/Dynastar ski for the same reason. As someone mentioned in an earlier thread a lot of Head/Tyrolia/Fischer athletes stick with the FF16 on Slaloms because it is slightly lighter than the 20. However on a GS, speed or free ski I have never noticed the binding weight as an issue and I think virtually all of my skis have metal race bindings - 1018s, FF17s, PX18, 916 Lab etc.