It's popular stuff. Most people think it's fun. It has a venerable history.
It bugs some sci-fi pedants. Even many of them don't mind putting the mind on hold and having some fun with it once in a while.
It's not easy to distinguish from soft science fiction, since it ostensibly deals with some human consequence of (vaguely defined) technologies. The only difference seems to be that space opera is lightweight, in literary terms.