It's hard to tell what the goal is in the picture- it's likely either a stewardship contract or a fuels reduction contract on government ground. Some of those contracts can be quite lucrative as the wood is usually sold cheaply and the contractor is free to market it however they wish. One contractor here made good money on a fire break contract by selling all the hardwood to a furniture mill.
I've never operated one but friends who have told me that being in the cab of a stroke de-limber for eight or more hours is brutal on the back, due to the jarring motion of the machine.