If it was a guaranteed accident like you suggest people wouldn't have done it for decades. Not the safest thing, but judging by the news it seems not even close to all the injuries weeks later from fireworks.
I've got to wonder if part of the reason it seems insane is because we've gotten used to single/dual generation households. If you light candles on a tree, then it's a commitment for you or your partner to be in the same room as that tree until the candles are extinguished. But if there is an older generation sitting around to be on firewatch, then it doesn't seem so limiting.