Fifth wheel safety chains?

I believe there is an underlying technical reason for chains on ball mounts and not on king pins. There is only a single size king pin, 2 inch and any hitch should work with and pin, SAFELY. But there are multiple ball sizes and someone can carelessly drop a 2-1/4 coupler over a 1-7/8 ball and the mistake is not visible, then a tail heavy load, a bump and trouble, hence chains. Has nothing to do with which type can haul more and even Andersen won't warranty stupid.