Cyrus Vance's argument
That Apple didn't have any breaches of its "locking" scheme prior to 2014, is like me saying "the US military doesn't need any encryption beyond WWII Navajo code talkers, since that was never breached".
Just because no one has ever picked the lock to my front door doesn't mean it is as secure as it could be, and I should retain the right to upgrade its security without waiting for someone to break in first.