(1) All robocalls in the state of California are illegal, period. Anyone who uses them is automatically a scumbag.
(2) Scumbags use the Do Not Call List *specifically* because it is the greatest resource of real, in-use numbers in existence. Legitimate businesses respect it, so if you're on it and you get calls, you know that this is the reason.
(3) Because both points prove that these people are scumbags, why would you trust a scumbag when he says that "pressing 1 will remove you from our list" or "call back to be removed"? All you've done is further solidified your number as an active lead.
(4) Yeah, yeah; "best $100 ever spent," whatever: Skype call blocking is free. But give me the ability to reverse power-surge a scumbag call and I'll pay $10,000.