"Rachael" and her company were caught, sued by the FTC, and shut down.
https://www.consumer.ftc.gov/blog/ftc-stops-robocall-scam
However, "Rachael" and her sisters were cloned by several other robocallers, all with different companies and phone numbers. More suits ensued. Here is one such suit, about a year later than the one mentioned above.:
https://www.consumer.ftc.gov/blog/ftc-gets-rachel-robocaller-again
So, the REAL answer is yet another question:
"Why should the scammers abandon a very successful technique, that so many suckers fall for?"
Rebecca at card member services. A clear scam. Takes a while to respond, robo voice and her opening message is "Hi! This is Rebecca from card services regarding your credit card. Everything is fine with your credit card but it is urgent you call us back to try to lower your interest rate..."