Facebook’s business model depends on user trust. If a simple third-party website could bypass their privacy settings, it would represent a massive security breach. Facebook employs thousands of engineers to ensure that if a user sets their profile to "Private," that data remains on secure servers, accessible only to approved friends. There is no "backdoor" for an external app to exploit. Ethical and Legal Concerns
Sites promising to unlock private photos or friends lists without a friend request often have hidden agendas: Data Harvesting: