Comment by extra88

Because the elements already exist. When the elements were invented and defined, CSS didn't exist and authors had to use elements to make presentational changes. When HTML5 was defined, CSS was well established and it was an opportunity to update element descriptions to get rid of specific presentational qualities.

There are lots of elements, if you don't find some of them useful, don't use them. Other people may find uses for the distinctions; even if they use distinctive styling for them all, they may need to document why they're used, not just for all the authors but for the audience as well; clearly we can't expect developers to know what all the elements are for so that's doubly true for the audience.