For a LOT of people, the happy outcome of the movie has a huge impact on how much they like it.

If Ethan Hunt was killed by the bad guy at the end of each Mission Impossible movie and the bad guy won and took over the world - you think they've have the same number of watchers? You think they'd sell as many tickets?

My wife watches all of those Hallmark Channel Christmas shows PRECISELY because she knows they will ALL have a happy ending. The shows themselves are different. How the couple finally overcomes whatever drama there is in the show to come together is different from one show to the next. But if she didn't know the couple was going to get together in the end - she wouldn't watch any of them.

Some people want to see the story of the football game, so to speak, but they want the story to have a happy ending.

You can slip a sad ending in on people now and then, and they'll keep watching. But if they notice that nearly every show has a sad ending now, they'll stop watching the channel.