Here are the reasons why:
* "Philosopher's Stone" was considered too highbrow or difficult for American audiences. Some thought the term "philosopher's stone" might be confusing or off-putting to young readers.
* "Sorcerer's Stone" was thought to be a more familiar and "magical" term. It evoked images of wizards and sorcery, aligning better with the book's fantastical elements.
* Marketing concerns. The publishers felt "Sorcerer's Stone" would have broader appeal and potentially generate higher sales.
Ultimately, the change was a strategic marketing decision, not a significant alteration to the story itself. Both titles refer to the same magical artifact in the book.
The change was controversial, and many fans, including J.K. Rowling herself, prefer the original "Philosopher's Stone." Nevertheless, the "Sorcerer's Stone" title has become the standard in the US.