Comment by Bartweiss

They work sometimes, sometimes people do rob you. That's still a thing that happens. So I lock my door to deter thieves, and buy insurance so that if I do get robbed I'm not doomed.

The NSA's statements aren't "we've lowered risk to an acceptable level, and put in safeguards for when leaks inevitable occur". They're "we're the only ones using this data, so there's no problem". That's provably false several times over.

To continue the metaphor, they didn't buy insurance because they trusted their home security so highly, and lately it's starting to look like they also forgot to lock the door.