Right, and so the PTFE is weakly adhering to the metal surface. Repeated hot/cold changes, scrapings (especially), etc., and as Iceman said, you're eatin' it. Fortunately, it's tasteless and will just pass right outta you. Amazing stuff.
But as for NASA, the problem I and probably the rest of the 60% have with it is that it's so bureaucratic... and political. They don't always make the smartest organizational or procedural decisions. But when they're on, they're ON!