What is the point of fastening the dogs to the sled in fan fashion?

From the text:

This construction enabled the weight of the sled and load to be distributed over the largest snow-surface; for the snow was crystal-powder and very soft.  Observing the same principle of widest distribution of weight, the dogs at the ends of their ropes radiated fan-fashion from the nose of the sled, so that no dog trod in another’s footsteps.

There was, furthermore, another virtue in the fan-formation.  The ropes of varying length prevented the dogs attacking from the rear those that ran in front of them.  For a dog to attack another, it would have to turn upon one at a shorter rope.  In which case it would find itself face to face with the dog attacked, and also it would find itself facing the whip of the driver.  But the most peculiar virtue of all lay in the fact that the dog that strove to attack one in front of him must pull the sled faster, and that the faster the sled travelled, the faster could the dog attacked run away.  Thus, the dog behind could never catch up with the one in front.  The faster he ran, the faster ran the one he was after, and the faster ran all the dogs.  Incidentally, the sled went faster, and thus, by cunning indirection, did man increase his mastery over the beasts.