Actually, the DNC list does work. Big and legitimate businesses do abide by it. Obviously, the scammers and shady businesses don't care about the DNC list. That's where the problem comes in, plus those exempt from the list (political calls, etc.).
I had a missed call from this number, message left about an exciting message about "How to put $10000 or more in your pocket in the next 10-14 days!" Yeah, no scam there.