How do the sanctioning bodies regard champions of competing sanctioning bodies?

I've noticed something interesting regarding the rankings of the sanctioning bodies. Obviously, we all know they are largely a joke. But, I've noticed that champions of the various organizations tend to get left out of the rankings of their competitors. For example, Cotto is the WBA champ but is not ranked by the WBC. Is this just more sanctioning body nonsense, or is there a rule where the competing organizations do not rank the champions of their competitors (that would still be nonsense, but you get my point)? Just curious, thanks in advance for the info.

Sometimes (or always) if a champ of one division , can't be ranked by the other. Obvuoisly each division wants their champ to be recognized as the best