It’s either this, or grow big enough fast enough before the cash runs out that they have a strong bargaining position with big cinema chains to cut deals for cheaper tickets, perhaps also using the carrot of some kind of concession promotion to encourage subscribers to buy popcorn etc.
If this model works, it isn’t exactly hard for a large chain like AMC to do in house at all, I really don’t see the incentive to get into bed with MoviePass. Some European cinema chains already do this, like Cineworld in the UK.