Can't someone luck out and jumble a bunch of numbers and letters, luck across a private key, and steal all the money off the paper wallet?
If it's pure luck, the odds are so astronomically low as to be pretty much zero.
And by low, I don't mean "winning the lottery" low. I don't mean winning the lottery while getting struck by lightning low. I mean like, pretty much zero.
Perhaps you mean winning the lottery while getting struck by lightning in the middle of taking a crap low.