What about if your iPhone gets stolen? A simple wipe using FindMyiPhone will delete all you data from your phone so the thief doesn’t access your data in your iPhone. But if remote wipe is not enough for you, then you might think “If you don’t have your iPhone back, no one will.” That’s when the self-destruct features comes in and explode your iPhone via Siri so no one in the future could use your iPhone, making it useless for the thief to sale it or keep it.
So thief, you will have to make sure to restore the iPhone 5 through iTunes before trying to unlock it by guessing passwords.