Mostly because that doesn't really "clamp" the hitch to the floor. That pulls the hitch down and the pin up to take the slack out of the operation. It also ensures that someone cannot inadvertently pull the pin and release the hitch. If you think that 40 lb.fts. of torque on a 1/2-13 bolt have any measurable holding power in the operation of these hitches, you're unclear on the operation of either of them. I have the B&W hitch and know exactly how it works, I don't believe you can say the same. :)
I have the Companion and would buy another if necessary. I don't think the Anderson is inferior, but it just "looks" flimsier. :) Just the impression I get when looking at it, I'm sure it's a very strong hitch and have seen the videos, but I can't shake that first impression.
I also wish to disagree with the person that posted "Sorry but chucking has EVERYTHING to do with the hitch...". I think that the position of the hitch in the bed may have something to do with "chucking" but I fail to see how a snugly fitting hitch of any kind will have any thing to do with "chucking". Provided of course that all other inputs remain the same.