tall tails

My dog has an extremely long tail which I guess is a positive with his breed.
I got to wondering why that is and have come up with a theory. He is a herding breed and the tail can serve to better balance him while running. The longer the stem to tip, the more balance he can have to take fast turns or look longer and block the sheeps escape.
I imagine the aussie, who is actually from the us, not the cattle dog or the kelpie but the shepherd with no tail, or I should say stem tail as all dogs have 3 vertibre on the tail stem, the shepherd must have a purpose to have no tail but, I can not fathom why. Why would one herding breed have points for long tail and another have stem tail? I must do more research.
The difference between breeds always astounds me. Then I wonder why there are size varieties to breeds, (ei beagle 13" and beagle 15 ") or why are there colors in the same breed (black and yellow lab) I know we breed for health, temperment and comform to purpose but, some things seem trivial at best. My dog just happened to have a long tail and of course he has a million great things about him, so I ask why bother putting this in the standard. Who knows why my breed is actually genetically the same as the black coated BSD but akc recognizes it separately while ukc sees them as one breed. If you send in a genetic testing kit you get variations on result too! In the us you may only breed the black coat with the black coat and the black and mahogany with the other Tervs yet in Canada you can mix them. It makes me think that Canada has a stronger gene pool to feed off of because you are more open to health, purpose, temperment breeding. I am sure I will learn later a logical reason for all this but, for now I just have to wonder why.