Personally, I'd want to have the source and run that software myself - how else could I trust that the app developer didn't bribe you or find an easy way to subvert your detection?
Valid point. Getting something you can scan for installed SDKs is pretty darn hard in many cases, so I doubt most people would want to set up and maintain something to do that for a few apps...
Unfortunately, this is one case where being open-source would probably make the scanner easier to game.