> Why not just wire the LEDs up to the same power line that goes to the camera?

It's just difficult enough to not bother considering the market doesn't care.

Webcams are typically USB 2.0 devices using generic drivers from the operating system or manufacturer. It's easy from a hardware and software perspective to send a command to the webcam to disable itself and turn off its LED. If you want to completely cut power then you need to add power switching circuitry.

You could use one of your CPU's limited GPIO pins to control the switching but now you probably need a smart power switch (~$0.30, which is significant) since the low voltage (1.2V?) GPIO can't handle switching a regular mosfet gate. GPIO writes are usually easy (just write to a memory address), but you'd still need to modify the vendor driver to do this and then distribute the driver.

Motherboards typically have embedded controllers which have GPIO - on desktops there is a SuperIO chip, I believe laptops typically use a regular microcontroller. Now you have some 3.3V GPIOs that can handle gate switching so you can use a regular MOSFET (~$0.10). You still need to modify and distribute the webcam driver, and now it might have to communicate with another driver which is handling the embedded controller.

Now you have to deal with the webcam disconnecting and reconnecting as you switch power to it. You want the device to always be present even if it's not enumerating on the USB bus, so you can select the webcam in zoom and turn it on and so you're not constantly playing the hardware connect/disconnect sound - even more driver changes. Maybe the webcam takes significantly longer to turn on now because it has to boot and enumerate.

That was all somewhat informed speculation, but I think it illustrates how a seemingly simple thing gets complicated. The electronics industry could easily solve these issues if there was motivation, but there just isn't.

Edit: Well, I'm posting this on an article talking about a vendor which is doing the work to make this happen. I guess I should say there's just enough motivation to eventually get around to solving this problem in a mature market.