I think it's just a convention among sheet-music publishers to do it that way. I've always assumed it was just to call attention to the title, as if to say, "Yes, this is really the song you bought." It may have something to do with the phenomenon noted in an article I once read, reporting that according to the proverbial "reliable study," the people who paid the most attention to advertisements for a given product were the ones who had just bought it.

Aloha,
Mark