Got it. Point taken.
Like, if I say, "Why are so many doctors in such a big hurry that they don't adequately pay attention to their patients' complaints?", that's a foolish inquiry, because there are as many reasons for hurried physicians as there are hurried physicians?
I don't think it's foolish to ask such a question, but I can see that, in the case of scuba instructors, the answer might be that there are indeed as many reasons for bitterness as there are bitter scuba instructors.
There is one thing foolish about all this, though, and that's that it's probably foolish to ask such a question on a forum full of scuba instructors.