(And making a trustworthy indicator that only shows if a recording is actually being created is basically impossible, so "camera running" is the only thing they could show)
Another option and even more trustworthy would have been a camera cover that was usable & durable and clearly & visibly expressed the status of the camera.
And the recording capabilities of the device were way overstated. Not just because of battery life, but heat. Trying to record video with it felt like putting yourself at risk of setting one side of your face on fire.
In fact, considering recent concerns with exploding batteries and the size of Glass and how hot it could get, perhaps the biggest marvel is that Google avoided even one Glass exploding.
The mere idea that someone could covertly record with Glass is silly, and there's tons of cheaper, far sneakier ways to film someone.
I get what you're saying, that average persons didn't know what the device could or couldn't do, but I don't think that's a justification to add a light that makes no sense to include.