MoviePass would have brought more viewers to their establishment. The customer would now have saved $10 on admission, and can now use that towards concessions. Since their concessions are basically 1000% markup, its pure profit for them.
I don't understand their complaint other than, they didn't think of it first.
No they're still making full price on tickets too, it's just that the money is coming from some VC that's willing to dump it for a bunch of data instead of directly from the customer.