Why is the tennis one armed backhand considered aesthetic form?

I have heard this twice, fans think the tennis backhand a thing of beauty. Roger was famous for backhand tricks, even though he had one of the great forehands,'
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Why this curiosity?

There is no natural motion of any east plains ape that required a backhand shoulder motion and the back of our hands cannot hold a throwing object.  We invented he backhand motion when we grabbed a stick, it is a purely human invention.