Yes, 50 million verified names and phone numbers of people who don't want to be called by telemarketers. So why would telemarketers even waste their time calling people who don't want to be called by telemarketers? Actually the no-call list is a benefit to the telemarketing industry because it essentially weeds out those phone numbers that the telemarketers would be wasting their time by calling. This way, the telemarketers can focus on those phone numbers that aren't on the no-call list. Also, telemarketers already have access to lists showing every phone number in the United States, so the no-call list is not a scam in any way.
Again, because the dirty little secret of telemarketing is that its profit margin depends on finding the weak-willed, the human-contact-starved, and the not-quite-all-there-any-more.
People who already want something will find the vendor on their own initiative. People who don't want something and have no difficulty in saying "no" will not be swayed by telemarketing. That leaves the people described in the previous paragraph as the telepests' bread and butter.
If such people can shield themselves permanently by taking one simple action, the whole scam dries up and blows away.