I know I'm late to this discussion, but the simple fact is that I won't pay for the entertainment in the main theaters because it isn't that good. The only reason as many people go is because it's free. If they charged everyone some kind of cover, then on a lot of ships the places would have far fewer people at a lot of the shows. I go because it's free, but I only go once or twice on a seven day.
And... as has been pointed out, we are already paying for the shows. Now, if they lowered the cabin prices... say $10 per day, and charged something for the shows then I would like that plan.
Memories of Naked Fanny