Why is Winston tortured but not killed?

Winston is tortured but not killed because the Party seeks to break his spirit and force him to conform to its ideology, rather than simply eliminating him. By subjecting him to psychological and physical torment, they aim to demonstrate their power and control over individuals, ensuring that he ultimately betrays his beliefs and becomes a loyal supporter. His transformation serves as a warning to others about the consequences of dissent. Ultimately, the Party values the manipulation of minds over mere physical eradication.