My Dad bought a 4" capacity chipper and mounted it on the front of a trailer, like the Bandit chip box combo. It works pretty well for him, but he's not a treeguy. He's a lawn service and does palms, which are really bulky, or bushes and small trees. He works out of a van
He mounted it so it would swivel as a turntable, but in the couple years he's had it he has never swivelled it once. Says you almost always feed from the curb-side and if the brush is coming from the other direction it's easier to just turn the whole rig around.
It's handy, he loves it as he can get rid of chips for free whereas anything else he pays to dispose of at the recycler. He says the entire rig has paid for itself just in the savings from not having to go to the recycler as well as not having to take the extra time to load, stomp and dice trailerloads of bulky small material.
I don't think it would be the right rig for many operations, but for the smaller companies the benefit of having your pickup freed up to take your tools and the logs gives you that level of economy and low overhead that's appealing. I very seriously considered a chipbox combo early in my career and think I would have been happy had I made that choice. I enjoy using Dad's setup when I go and work down there on vacation.
p.s. the attached picture is of Dad and a lady across the street helping chip. I've already addressed the lack of PPE, so no commentary on that is needed.