Docking the tails of Cocker Spaniels

I am expecting a litter of pups on July 19th. I'm pretty sure I know what I'm getting myself into. I've been present during the birthing of pups before. I bred Amani with a handsome fellow from El Shaddai cocker spaniels in Cherry Valley. She's agreed to teach me how to dock the tails (the breeder, not Amani), so that will be new for me. I've never cut off the tail of a dog before. Sounds horrible but I guess it's not as bad as cutting foreskin from our little baby boys. I was wondering why the practice was started and found through some reading that there were practical reasons to do so. The reasons varied depending on the breed. Some of the reasons were:
1. guard dogs, to prevent them from being grabbed by the tail
2. herding dogs, to prevent feces from building up in the fir.
3. hunting dogs, to prevent tails from getting tangled in the briar thorns and thistles
4. Terriers, it makes a stable handle to grab the dog and pull it back out of the burrow.

I"m sorry to make you think about cutting off tails but I think it's important to understand why we do things. Also, for those who believe it to be a horrible practice, it's necessary to know that in those countries where tail docking has been banned there has been a tremendous increase in the number of severe tail injuries requiring emergency docking when the dog is an adult. Tails are very hard to heal for two reasons. Anyone care to take a stab (no pun intended) as to why that is?