Why can't koch's postulate work for virus?

Koch's postulates are criteria established to identify the causative agents of Infectious Diseases, primarily for bacteria. However, they cannot be fully applied to viruses because viruses cannot be cultured on standard nutrient media, which is essential for demonstrating their presence in infected hosts as required by the postulates. Additionally, viruses can exist in a latent state and may not always cause disease in all infected individuals, complicating the ability to link them directly to specific diseases. Thus, alternative methods and criteria, such as molecular techniques, are used to establish viral causation.