George, my understanding of human nature is that we do almost everything arbitrarily. The few things we are driven to do are themselves fueled by the arbitrary things that have happened in our past. The only reason any of this is happening that anyone can convincingly point to is the big bang.
Also, I would never encourage someone not to ask. The fun is in the asking, even if there is not absolute answer to be divined. The "don't ask why" is simply part of a quote about an idea which seemed relevant to me.
So you disagree with the view that we have choice in what we do, and that is why there is the concept of ethics/morals/reason, and so people are put on trial for rape, child abuse, murder, theft, etc.?
I can understand not asking a plague, for example, why it does what it does: it cannot answer, and nor can it choose what it does - it just is
; people, however, can and do choose, hence the question being asked in the first place.