Yeah, I sort of figured that if your optic fails, there is a chance that it's not gonna be "see-through" anymore. Its not just dead batteries, but mud/dust/scratch/fog/whatever, that might make it easier to remove the optic, and have a SOLID set of sights ready to go.
I am not even a hobbyist though, as I think that implies far more time and money spent than I have
E.T.A. After some thought, I realized that it may have to do with maintaining the same cheek weld.