How about I chainlock your front door because someone thought he saw a burgler in the neighbourhood. I have the key and am always available down to block. Not to piss you off, just as a security measure.
What does this have to do with anything? Forcing users to change their passwords every 15 days to a 15 to 30 character password composed of no dictionary words, mixed upper- and lower-case letters, special symbols (except '^' and '$') and at least four numbers that do not appear in their SSN or birth date is a security measure too. Doesn't mean it's sensible or even reliable security.