People in the hard sciences do often listen to people outside the hard sciences, because it's comparatively easy to tell whether their work is sound or not. (Almost always not.)

I agree that the social "sciences" are different, but that's because they're not actually science.

When your theories are heavily tested by evidence, you just don't need all the drama and gatekeeping nearly as much. That isn't to say that there's none, but it's not hard to get a decent hearing if the material is actually good.