I also thought about another point recently. Many companies hand out Apple laptops with pre-installed software to their employees. It's not entirely unrealistic

I also thought about another point recently. Many companies hand out Apple laptops with pre-installed software to their employees. It's not entirely unrealistic to imagine that some of the pre-installed software is intended to spy on the employees to make sure they don't use company hardware to do anything weird and takes screenshots and camera shots occasionally. In this kind of situations you'll see the LED and you'll know what's happening and you'd much prefer to have a physical cover on your webcam.