Then why are they framed as realistic questions? Sure, the most secure way of handling them might be what you suggested, but that is not how they designed to be answered. Security questions are created to verify your identity when password does not work (e.g. when they are forgotten). Answering them in unrelated ways just create another password that will also fail under the circumstances that security questions are needed.
The problem is that security questions are fundamentally flawed. Most of them are easily guessable with a little bit of research, and because they can often be used to bypass your password they're effectively a backdoor into your account. You're generally better off using them as either a backup password (that is, not guessable even given knowledge about you), or simply not using them at all. If you forgot your password then reset it via your e-mail account. In short, don't use security questions, they're fundamentally broken.
