I can’t imagine a movie theater using a rear projection screen. If someone were to pay the high cost of a movie ticket and then be unable to see the movie very well because of where he sat, then I imagine he would be very angry.
Every theater I’ve ever been to uses a front projector in a room behind the seats. If you turn around, you can see the high window from which the image gets projected onto the screen.
I’m sure hot spots would be big annoyances as well. It’s hard for some people to focus on the plot if there is something on the screen that doesn’t belong there distracting them.