> Once powered off, the data is only recoverable for a short time
It comes down to defence-in-depth.
That short time is usually between seconds and minutes.
A can of compressed air can extend it a bit, but a dip in liquid nitrogen can turn the dial up a long way. Other techniques may appear in the future.
You need to trust that one of your own people won't do any tampering to extend the RAM. Much easier to verify there isn't any on the way out the door.
