Why are expandable broadheads not allowed? Wouldn't it mean a quicker, cleaner kill?

Expandable broadheads were first made illegal for big game hunting in Idaho during the early 1990s. At that time there was broad public opposition to their use and concern about the "failure rate" of some of the early models. In 2006, the Idaho Fish and Game Commission evaluated all archery and muzzleloader equipment restrictions. While adopting some changes, including allowing the use of higher let-off bows, they chose to not remove the restriction on use of expandable broadheads. The Commission strives to balance reasonable equipment restrictions with ensuring biological management objectives are being met. Public comment received over the past few years, and discussions with organized sportsman groups,suggest the archery hunting public is still divided over whether to allow the use of various technological advancements in primitive weapon hunts.