why does my radio not power off when the car is off causing a dead battery

Hello, sounds like there may be a concern where the vehicle is not seeing the driver open the driver door. The sensor at the driver's door can corrode or become a concern. If this happens, you will not easily know if the door is reading open or closed unless you use a diagnostic tool that can component and sensor operation This could indeed drain your battery as with any accessory potentially involved that is staying active after leaving the car. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops