Jobs. Here is a short explanation about feet. http://www.canismajor.com/dog/feet.html Some is related to job, some is ancestry. Most webbed toed dogs have mountain dog ancestry. Most hare footed dogs have some sort of sight hound or runner ancestry. A tight compact terrier foot. Most types have tight or loose examples. Think of it like this, do you think a runner with really flat feet or good arches would be better? A tight foot is a sound foot.