TidBITS: Stewing Over Safe Sleep:
Imagine that you've just bought a new car, and the car manufacturer has thoughtfully included a new piece of technology, a Dead Battery Preventer. In order for the DBP to work its magic, your car must continue to run for 49 seconds after you turn it off - every time you turn it off - during which time you can't open the doors. But, as the car dealer reassures you, surely this is a small, barely noticeable inconvenience compared to the tremendous savings in grief you'll experience on those occasions when you'd otherwise find yourself stuck, unable to go anywhere due to a dead battery. No waiting for a tow truck to arrive, no frantic calls to AAA. Just activate the DBP and drive away.
There's no such thing as a DBP, but that's the closest analogy I could come up with for a feature that has been built into all Apple laptops for the past couple of years.