Why the SCP Foundation keeps ballistic-missile submarines

Why would the SCP Foundation send an SSBN instead of an SSN?

Its ballistic missiles provide a nuclear option when containment fails and an anomaly must be destroyed in a broken-masquerade scenario.

The use of an SSBN prompts a question about whether an attack submarine would be more appropriate. The ballistic-missile submarine has a different fictional role: it provides a nuclear option if an anomaly escapes control. Some SCP timelines describe local SSBNs firing at an anomaly after containment and secrecy have broken down. That explanation distinguishes an emergency strategic-weapons role from ordinary pursuit or observation.