Video isn't just about pictures,
it's also about sound.
Without the audio you would have to guess what this film is about.
Frustrating, isn't it?
Not knowing what's going on.
That's the situation for everyone who can't hear.
Captions make videos accessible.
Which is also handy for people who want to watch video in loud environments.
Or where you need to be very, very quiet.
Web accessibility: Essential for some, useful for all.