One reason seems to be that the calls seem to be made by fly-by-night call centers and are selling as 3rd party affiliates of otherwise "legitimate" companies.

One reason seems to be that the calls seem to be made by fly-by-night call centers and are selling as 3rd party affiliates of otherwise "legitimate" companies. I use quotes around legitimate because they really aren't legitimate. But they work enough at arm's length to the crooked call centers that they manage to avoid getting shut down. This is very common practice in a lot of scams now. I think we need some new legislation requiring the vetting of affiliates that bring in more than X dollars.