My old coop did that.  It makes sense to me, but I am not a small producer.  It made a lot of the small producers complain and switch companies.  I think the hauler and possibly the coop was OK with that.  The hauler has to stop there and pump for very little income, possibly a loss.  It takes time to drive a couple miles out of his way and time to back up, hook up, set up wash etc for a few hundred or thousand pounds of milk.  I think I am getting charged around $0.45/cwt.  So I he stopped in to pick up 2000 lbs of milk he is only making $9.  It may add 15-20 minutes to his route.  A truck can't make money at that rate.  Raising the hauling rate will mean the big producers are paying more so the little producers can still get picked up.  It's also more paper work and more field men they need to cover all the farms.  It seems unfair but it is a business and they are treating it as such.