It appears that you are under some misconceptions as to what the DNC does.
Does the DNC prohibit calls from legitimate telemarketers?
Yes. When was the last time you received a call from a legitimate telemarketer?
Is the DNC a call blocker?
No. even though the calls that you may receive are from criminals, do you really expect criminals to subscribe to the DNC?
So, the DNC does what it should, that is prevent calls from legitimate telemarketers. However, political calls, calls from charities, surveys, and debt collectors are exempt.
This is at least the fifth or sixth call we've received of this type from many different numbers. Today is was (347) 394-1518. I actually returned the call, told them I knew it was a scam, that I had already reported them to the IRS and to never call me again. Then I promptly hung up. I keep blocking the numbers when I can, but is it very frustrating.
Same issue. Fake IRS. Claimed to read my affidavit and threatened arrest. Even though I was partially fooled by this scam, I hung up before any money was requested.