Including captions can help the hearing impaired enjoy your video. It can also help people understand the video if it is being viewed in a noisy environment such as a shopping mall or airport. Further, captions can help people retain the content of the video better as the audible portion is reinforced with text they can read. Finally, when people view videos on social media feeds, they often watch the whole video without clicking to turn on the sound. If there are no captions, these viewers will quickly lose interest and scroll on past your video.