They probably have a deal with your cable company that provides your router.

Why would your wifi be served from a box provided by your ISP? That's a bad idea.

There's been cases where TVs sent data signals back to the cable boxes over coax. There's now high-frequency, outside-human-hearing ID triggers the that are released into the air and ‘heard’ by smart phones with proprietary apps installed with trackers and too many permissions allowed. They can even send out signals via gyroscopes.