It's not as much fun to watch movies alone as with friends. But it's easier to get friends to come over and watch a movie if you've already seen it. For example, suppose you want someone to see the Woody Allen movie Stardust Memories with you. You have to admit that if they'd never seen one of his films before, Stardust Memories would be a poor introduction. Few people could watch it without fearing they were missing some crucial in-joke.
But now suppose you've already watched Stardust Memories with your friend. Now when you say "Let's watch it again," they know what they're getting into; and once they've seen the film twice, they may well agree a third time is worth doing just for kicks. So on the whole there will be more people willing to watch a movie twice than once; and if there are more people willing to see something twice than once, then it's easier to find someone who'll go out of their way to see it the first time.
More generally, watching movies in the privacy of your own home is where most of us can be most adventurous in our viewing choices. It's where we can take chances we wouldn't otherwise take: mumblecore, or Bollywood musicals,