It's a part of marketing.
   When you run a business, you have to know who your stereotypical
   audience is expected to be. These are all generalities of
   course; you may find your ACTUAL audience turns out to be _much
   different_ than you anticipate, but it helps shape your focus
   better than, "THIS IS GREAT FOR EVERYBODY", which... it probably
   isn't. I mean, it _might be_, but few books, businesses,
   schools, TV shows, religions, sciences, ideologies, messages,
   art, music get that status.