Saskatchewan-based Steven Lewis had a fascinating take on why evidence plays a smaller role in decision making than many would like. Behaviours respond to incentives. Most systems pay for both kinds of behaviour. Experience trumps probability. Avoiding adverse events is more important to a practitioner than consistency with research evidence, and in any case, statistical conclusions will always be subordinate to the particular cases.
Methodological purity breeds suspicion.
A randomized, controlled trial is an abstraction from real world messiness. Publication is not the same thing as communication. Standard methods of communication are the least effective. The focus on brevity and numbers by journal editors actually impedes information dissemination. Unregistered trials and publication bias enable critics to ignore good science, and what interests the scientist does not necessarily reflect the interests of policy makers.