They could easily sell the pieces separately, but they won't. They say that they are not willing to break up the kits because they won't make as much money due to people copying or modifying the parts. They feel that more people are going to be taking their stuff and making money off them indirectly. I had a friend a couple of years ago wreck his tracker with the Calmini 3" and I called Calmini to get replacement front arms because they got damaged, they absolutely would not sell the arms separately! He had to buy a new kit!
Personally I think that part is crap! But in the same token, I understand where they are coming from, just look at how many zuki things that different people have copied and made money on over the years!