I see it like the judicious use of signals intelligence in WWII. If you use it for everything, you risk tipping the enemy off that their crypto is broken. You

I see it like the judicious use of signals intelligence in WWII. If you use it for everything, you risk tipping the enemy off that their crypto is broken. You have to balance the benefit from the inherent knowledge leak from using it. I'm not saying they have it, but if they had it, they would be foolish to use it all over instead of only on key targets.