If the camera light does not flash when the built-in flash of the camera is not turned on, why?

The studio flash used in the photography studio is controlled by the light emitted by the flash on the camera to trigger the photosensitive trigger element on the studio flash. So if you don't turn on the camera's built-in flash, there will be no flash to trigger the studio flash to shine.

At present, a wireless trigger is also installed to control the flash of the studio flash. Such a flash device does not need the built-in flash of the camera, but the camera needs to be equipped with a wireless trigger to control the flash of the studio flash.