Lol,it doesn't hinder their speed/agility ?
on average, Nope.
there is contrversy asto bobbing after they learn to walk bc it messes their balance up, but there are also confirmations to older dogs having to have the tail removed or part of it removed bc of injury and they never knew it was missing.
iv also heard speculation that it may hurt them physicaly though if they are bobbed to close to the spine.
its just dealer choice.