Simple, ignorance. In the three years I have had it, it has been more of a hurt than it has a help. The track version would be awesome to have, but 9 tons per wheel with a contact patch of maybe three inches, is simply stupid and poor designing.
I've seen a few local guys that swapped out the two rear wheels for tracks to solve that problem, the one fellow said it eliminated 90% of the problems they had with it but god save you if the front wheels ever touch a soft surface.