Why do you have projector in scare quotes? And what makes you think they don't screen the movie? Exhibitors have a contractual obligation to show movies a certain number of times a week, and the media players that run them show receipts to the studios ... it would be surprising if they didn't actually do that simply because nobody bought a ticket.
Probably just showing that it's not a film projector, but in actuality, it is still a projector. It may be assumed that digital movies are shown on a giant display, but that's cost prohibitive at that size; it's still a blank screen with light projected onto it.
