Another use is for low light visibility.
Lenses gather light, the large the diameter, the more light they gather.
Given the right lens and coatings (or lack there of), things not visible to the naked eye at dusk type conditions are visible through the lens.
Funny thing is that the cheaper lenses tend to work better for this. They generally don't have the Infrared coating so don't block it.
I read about his a long time ago that the cheap digital pocket cameras tended to work better than the more expensive cameras in low light conditions due to their lack of IR filter coated lenses.
I tried it out with the one I had and it actually worked. It's easy to tell if it has an IR coating or not by looking at a TV remote while pushing a button. If you can see the light, it doesn't have the IR blocking coating. Mind you, this only works with cameras and not direct optics. The sensor in the camera detects the IR light where-as your eyes can't.
As far as your bino's and scopes, take a peak around dusk when you can barely see with your eyes alone and then again through them. I think you might be mildly surprised.