Doug, we added the Sunday morning weigh-in in recognition that a significant number of Juniors & Cadets are actively involved in spring sports for their schools that might make the evening weigh-ins unavailable to them. Since the weight classes are all fixed, we can relatively quickly redraw the brackets and still start on time.
We considered doing the same for the younger kids on Saturday, but decided that the concerns over starting the tournament timely outweighed the benefits for this age group. Since we have to group these weights classes, there is more time involved in first deciding how to split the brackets, then redrawing them. In addition, these age groups are not typically locked into the same commitments that the older kids are.