I'm not saying intentionally influencing ladder positions, but the opportunity is there for some teams (Carlton and Collingwood as I have mentioned) to benefit from the good run provided by the umps. It could be as simple as the umpires' coaches mentioning to umpires that certain players are being regularly held in marking contests and to be aware of it. McKay and Curnow the obvious ones.
Clarry and Josh Kelly get held at every stoppage but rarely get frees for it. Guess the umpires coaches don't talk about it.