Many of the passwords I currently use have been randomly generated and are stored in a password storage app, the database in which these passwords are stored could be easily lost, damaged beyond recovery, or to which I could forget the master password.
So, if legally required to produce a password for some reason, I could quite conceivably go to jail even if I were willing to provide the password, but just couldn't remember what it was (or if it was one of the randomly generated passwords that I'd never memorized in the first place but no longer had access to for some reason).