*edit* LOST and I were typing at same time....glad we came up with basically the same answer
There is always a struggle between the known and the unknown yardages. The ABA introduced a "range finder" class and it ran for a couple years....the participation was less than thrilling, in fact it was dismal to be honest. Some shoots had two participants.
So the inference was drawn back to that experience and the decision made that rangefinders would not be included.
Look at it this way, if you shoot fixed pin (I do) you can basically eliminate an entire pin or two...most people have 20,30,40,50,60. This class maxes out at 40 yards....so you have a 20,30,40 yard pin. That helps immensely in having to judge a yardage knowing the furthest possible shot is 40 yards. On the flip side, I would hazard a guess to say when someone sees a target at 20 yards they know it's a top pin shot....I shot "Hunter" class last year when offered and at provincials and nationals, my sight had 4 pins and I only ever used 3 pins throughout the entire season during competition.
The main idea of 3d is (or was) to practice for hunting. What better way to learn and make mistakes but on a fun shoot with foam critters. While I respect those who really want to have rangefinders included. The 3d committee consulted and the general consensus was to not have rangefinders...that decision was not unanimous
Not everyone has a rangefinder...BUT everyone has the potential to become better at judging range.
LC