Personally it doesn't matter too much to me either way if a celeb does or does not promote a product. I have never been the type to cut my hair in a certain style, buy that bag or dress, or try the new thing just because a celeb is now doing it.
However I do know that some people, especially the younger generations are influenced by celebs bc they view them as role models so if they can encourage our kids to be healthier (mind, body, hair, etc) then I'm all for it. No matter what I love seeing naturals whether they be famous or the girl in the supermarket with that fly twist out!