Well, let's see... there is no law saying MVPDs must pay for retrans. Aren't they free to say "we won't carry you"? Did you ever think MVPDs feel the price they're paying for locals must be worth it? Otherwise, why pay?
What stops Charlie from saying "We won't pay one cent for your station."? Oh, wait, he'd lose customers.
I think it's great that Dish allows you to opt out of locals. You don't even need an OTA antenna to do so.
ETA: In order to fully do away with retrans, wouldn't you need a law saying stations couldn't charge it?