Widely Used But Untested Interventions

When reading this Physiospot Blog entry on Neural Mobilization it brought to mind a question I've had many times over the years.  What is it about Physical Therapy that interventions become so widely used without undergoing any kind of rigorous testing or trials?  Whether it is low-level laser, myofascial release, neural mobilization or anything else for that matter.  We seem to willing to take it on the word of some device manufacturer or even worse some self appointed guru that their interventions work.  How do we know?  It sometimes seems to me that not only do PT's seem to have some innate "peace gene" but seem to have lost their "skepticism gene" somewhere along the way as well.