While this is often true, sometimes accessibility features can be distracting to those who don't need them so should be implemented in a way that they are optional. For example, closed captions intended those who can't hear at all contain much more than spoken lines and are not appropriate for learning the (spoken) language and even less so when watching something in your native language with a good audio environment. Which is why subtitles are not on by default and you have different tracks for closed captions and regular subtitles.