It's a numbers game, I'm sure. 99.9% of the population won't fall for the scam, but they only need one. Unfortunately, it's most likely the elderly that will fall for it.
My mom is 85 and pretty savvy, but no matter what I say she almost always answers the phone, even when the caller ID says 'unavailable' or 'unknown caller.' She then tries to have a conversation with the caller explaining why she's not interested in whatever they're selling; or in this case scolding them for trying to scam an old lady.