A few days ago, I saw a little thing circulating around Facebook about how, 22 years after its release, people are still arguing about the title change of Harry Potter and the Philosopher's Stone to Harry Potter and the Sorcerer's Stone for the American version of the book.
As a writer, having been to various classes and workshops about publishing, I understand that to a certain extent you have to be concerned about whether a title is marketable. For example, the film version of a certain Stephen King story was changed from Rita Hayworth and Shawshank Redemption, to The Shawshank Redemption (which, admittedly, is still a mouthful). Likewise, the novel Fried Green Tomatoes at the Whistle Stop Cafe became simply Fried Green Tomatoes for the the film version. However, these changes were made so that the title was shorter, more easily accessible - someone walks up to the ticket counter and asks for two tickets for Shawshank.
In the case of the Harry Potter example above, it wasn't just the title that was changed. On several occasions, British words were switched for American words; the quaffle is described as being the size of a soccer ball rather than a football, and at one of Harry's quidditch matches he's cheered on by a banner that says "Potter for President." The mentality, in the late 90's when the book came out, was that kids weren't going to read a book with unfamiliar British terms, that the word "philosopher" was boring, and kids would be more likely to read a book with "sorcerer" in the title*.
*This leads me to ponder if the book would have received less challenges had the title been "philosopher."
I find it particularly intriguing that the title was changed from "philosopher" to "sorcerer" because the Philosopher's Stone was a "real" thing. In the middle ages, during alchemy's heyday, it was thought that it was possible to create a substance, an item, that would transform any metal into gold, and that a side effect of this process created an elixir to prolong your life or make you immortal. (Not sure who came up with this idea - "hey, if I tinker around with a bunch of metals and salts and things I'll just randomly come up with this magic stone that does all this cool stuff.") This led to a large chunk of students in my college humanities class suddenly gasping amongst themselves during a lecture, "What? It's real? She didn't make it up?"
I can see why some titles are changed for sake of brevity, or to inject a recognizable character - Indiana Jones's name was added to Raiders of the Lost Ark when the second film was released. Harley Quinn's name was added to some listings of the recent film Birds of Prey out of a concern that the poor opening weekend meant that people weren't aware who the movie was about.
But in Harry Potter's case, I honestly feel that this is a case where changing the title was not needed at best, and possibly detrimental. J. K. Rowling built this world balanced firmly on western mythology and canon. The books are peppered with well-known (and lesser known) characters, creatures, and plants from mythology and literature. Why dumb down the title for kids? Kids are smart. They'll pick it up. They'll eat it up. As Robin Williams said in Mrs. Doubtfire, "You don't have to play dumb to them."