I think non destructive testing methods like dye penetrant inspection are ideal in a variety of scenarios. It’s understandable that they are in widespread use when dealing with metals and such.
However, I think that depending on the context of the work being done, you might want to consider more effective inspection methods. For example if I were inspecting the wing of an airplane, I wouldn’t trust dye alone to be the sole method for inspection.
I would use a method that used some kind of technology – sonar or lasers or whatever – to bounce against every bolt and seam of the airplane wing to ensure that it’s solid and sound. I’ve heard of cases where planes have crashed because of loose bolts or because flap panels came off. With airplanes I think you have to use the best inspection methods possible.