Ok, so there are good reasons to use lights and apparently they don't spook deer as much as I would have guessed. I too carry a light for emergencies, maybe signalling to rescuers after I've fallen in the dark and called for help. I don't have to worry about other hunters or bears, and my land isn't so big that I can go more than a mile without hitting a fence. Also someone mentioned going far enough to avoid other hunters, so I guess they haven't got a stand sight picked out, just looking for one.
I appreciate the serious answers. I had not thought of many of the problems encountered in different places and situations. I live in an area with small farms and it is unusual to cross a mile section with out encountering one or more fences a creek or field edge to follow. Now I know why all the people I take hunting from other states use lights, which seems silly to all the locals here.