probably because the cable company owns the box and has removed your ability to connect the box to your computer.
or
the cable box doesnt have a physical connection between the hard drive and the usb or ethernet connection.
you simply cannot transfer the data if there is no physical connection between the hard drive and the usb/ethernet socket.
that means you need to get in there with a soldering iron to solder the outputs to a wifi device (or some other wireless device)
nobody is going to be soldering on their cable box and expect the cable company to give them zero hassle.