From a provider standpoint, I’m guessing they would lose more revenue from existing subscribers not using it vs. what they’d gain from new (often dormant) subscribers.
It's a great model for any younger, relatively unknown provider for this reason. Although, the $9/mo Netflix subscription (I can't remember the actual price point, but it worked out if you watched more than 2 movies in a month) totally beat the pants off the Blockerbuster late fees / missing title fees on a $1/film/day pay-as-you-go model, from a consumer standpoint.