Why does the alarm go off when you use your valet key?

The alarm goes off when using a valet key because the valet key typically has limited functionality compared to the main key. It may not deactivate the alarm system, which is designed to protect the vehicle from theft. When the valet key is used to unlock the car, the system detects an unauthorized entry and triggers the alarm. This feature is intended to enhance security by ensuring that only the main key can fully disarm the security system.