Question

Why are majority opinions useful beyond simply sharing the supreme courts decision on a case

Answer 1

Because the majority opinion sets forth an explanation that details the rationale used to formulate the court's decision, and as such becomes part of the body of case law, it provides a valuable reference to be used to predict the outcome of future cases. It also reveals which points of law were most prevalent and the manner in which they were analyzed so that the written law is better able to be interpreted.