Dog spinning in circles - what does that mean?

I have occasionally met dogs that have habitually chased their own tails. They would spin in circles. I was curious as to what causes this so I tried to look it up. Some people and dog trainers put it down to dogs that are raised in kennels and don't get out often enough. They assume that the dog learns to spin in circles as a way to combat boredom. Unfortunately that does not explain the dogs I have known to spin - they never saw the inside of a kennel or even a dog carrier. I do have another theory.

I have a dog that I have to put on a tie out cable when the electric company comes out to read our meter. She is on the tie out for about 1-2 hours on the date of the visit. She is not fond of the meter reader since she doesn't like people snooping around "her" house without her owners around. One day she had to go outside to poop and I put her on the tie out, just in case the meter reader showed up. Sure enough the meter reader was there about 5 minutes later and I saw my dog spinning on the end of the cable. The meter reader got back in his truck and left and then my dog got loose! She only followed the truck to our property line but I then had to fix the cable tie out. I had a set of small hoist rings and used one of them as a temporary ring. It was then that I realized that maybe the dogs that spin had been on a tie out at one time in their lives and learned to spin to break the chain or the connectors. If that is the case then those dogs are pretty smart.