Because it conveys information?
If you care about the characters, you'll care about their dialogue.
See Plinkett re: Rogue One. There's a scene where whats her name and Andor fight off troopers (too easily, I add) in some alley.
It's wordless. It's just action. Just moving pictures. And it was so. fucking. boring.
Compare that to the scene where Luke, Leia, Chewie, and Han are in the prison cells. They're deep in the beast, they're sort of a match for the troopers, but are pushed back. There's panic, there's questions, there's plans being made up on the fly.
We care about the dialogue there because it conveys the situation, gives us answers, and we actually gave a damn about the characters as they were being pushed back, they couldn't really fight their way out of it.