I suppose that's true, although competition bikes would have chains checked far more regularly that some daily clunker.
I've had a nearly new Izumi chain snap on a 200cc Honda but that just unrolled onto the road, luckily. Then again, I've seen a few rewelded C range Triumphs where the chain has bunched around the gearbox sprocket and damaged everything in the area...
(the later ones even had a little chain guide fitted in this area to allow the chain to roll off)...to it certainly has/does happen.