My girl and I are often browsing through the movies we have, but there are quite some movies we never really checked or can’t remember whether we actually watched them. Watching the trailer would give us an idea whether this is something we feel like watching now or whether it’s a movie we saw before.
There are already random trailers before watching a movie, but to us it would be more useful to have the option to just watch the trailer of the movie itself. Not before the movie of course, but maybe just a button in the “movie detail” interface. Something like this:
(nevermind the movie, it was the only clear image of the (although outdated) user interface of my tv i could find, haha. but you probably get the idea).