Hermione erased or altered her parents’ memories to protect them from the dangers of Voldemort’s followers during the Rise of the Death Eaters, and to keep them safe while she and Harry pursued Horcruxes. The motive was protective and strategic: if Voldemort or his supporters learned of Hermione’s family, they could be targeted, used as leverage, or harmed. The crucial nuance is that in the books Hermione states she modified their memories rather than fully wiping them clean, and the implication is that their memories could be restored after the war. In the films, however, the depiction often presents Obliviate as a memory wipe with less explicit discussion of restoration, leading to a common misinterpretation that the parents were permanently erased. Key points

• Reason for memory alteration: protect Hermione’s parents from being targeted by Death Eaters and to shield them during the war (a contingency to ensure their safety while the trio hunted Horcruxes).

• How it was done: Hermione used a memory-modifying charm for her parents, and in the books she explicitly states she “modified” their memories rather than completely erasing all memory of her, with the understanding memories could be restored after the danger ended.

• Difference between books and films: the books describe a temporary modification with the possibility of restoration; the films sometimes present it as a more permanent or less clearly restorable act, contributing to fan debates about whether the memories could be recovered.

If you’d like, I can pull up more detailed passages from the original text or reputable fan and critical analyses to illustrate how this moment is depicted differently across media.