They're likely doing this to manage cost. If somebody wants to see The Avengers twice but they can only use Moviepass once then that's less money Moviepass has to pay out if there isn't another movie they wanna see next week. They have to make these changes otherwise a year or so from now the company won't exist anymore.
You can't give people unlimited movies one a day any movie for $10 a month and expect to turn a profit unless you own the theater it's being shown in.
Sounding less and less worth it
I'd say 4 unique movies a month at $10 is a great deal if you regularly go to the movies. Even if you only go once a month that's damn near breaking even on your end.
The offer they have right now is what they should have came out with in the first place. One movie a week no repeats. Many places a non-matinee movie ticket is $7-$9 so at two movies a month a customer came out ahead. The reality is almost nobody is gonna to to the theater 4 times a month. Many people will struggle to pass 2 times a month unless it's summer blockbuster time. If Moviepass can negotiate the theater ticket price down to $3-$4 or so a movie they'd be good. At least they wouldn't lose money on the average customer.
Moviepass is like Planet Fitness. Most Planet Fitness gyms have far more members than the gym can support. Half their members never even go to the gym but still maintain that $10 a month because idealistically they want to go but are too lazy to force themselves. The guy that goes to that gym regularly thanks them because that's why he can get a $10 a month membership to a gym. People subsidize his membership.
That's what Moviepass needs. A plan that encourages people to sign up because they cost is low but that many people won't take full advantage of so the company can make money.