Owen and Beru died such horrible, undignified deaths really. They were shot and killed whilst in the throes of terror that their adopted son would be next, and then their bodies were dumped outside and burned.
Luke regrets their deaths terribly. He regrets that he wasn’t there to save them, even though there was probably nothing he could have done, and he deeply regrets that his last conversation with them was so charged with resentment. He knows they loved him, but there’s an awful lot of sadness there.
Luke doesn’t know, but he sort of suspects, that after his aunt and uncle died they were greeted by a familiar brown-eyed woman with flowers in her hair. “Thank you for looking after my son,” she said, hugging them.