People tend to really misunderstand how it works and generally do not understand that the dnc does not protect you from the scams,frauds,extortionists and the unscrupulous nasty's that refuse to obey laws. Charity's and political, along with some survey's are exempt from this. Most of those will place you on the their internal DNC if asked though and there is a political DNC (it works very well too I might add) list you can sign up with.
Complaints filed with the DNC and other agency's are used to establish a pattern, then they can take action. They do make busts, they do fine them, and they do make arrests. You also need to realize that some of these bad actors are located in foreign country's and then their government has to work with ours. Slow it may be, but it does happen!
The more complaints filed, the more info they have to go on!