The answer is written by the OP, in such a way as to give the impression that the answerer and the OP are different people, so it took me a little while to realize. Móż pointed it out also.
The problem that I see is that the question asks, in essence, why a given technical term does not have different way of calculating it. Many users have given answers that essentially explain why it's the way it is. The average is the distance / time.
People have perhaps been misled by the question in the title. The body of the question asks something quite different. It's a rambling discussion that ends
I don't care about time anywhere here (minus speed) -- the definition of average speed doesn't bother me, I'm just wondering why this isn't a more widespread metric.
In retrospect, I think this question should have been flagged as unclear what you're asking, and closed.
The current issue, as I see it, is what to do with this answer. In my view, it takes a straight forward mathematical calculation and coerces it into a statistical framework, which is then miss-applied to support the OP's thesis. In my view it's factually incorrect.
In my understanding, this site is meant to be striving to provide the best possible answers to answerable questions. The answers to some questions are a matter of opinion. Many answers cite experience. But overall we strive for the best possible answer.
In my view a factually incorrect accepted answer should not be on a SE site.
So the question is - what to do. Delete the accepted answer? Get off my soap box and ignore it? Delete and close?