I've learnt this one from my other half: she rarely takes pictures because focusing on pictures detracts from actually living in the place. She takes pictures as a sort of "index" for where we've been: a quick of us together with the location in the background, maybe one or two snaps of beautiful sights, and so on. It's pretty rudimentary, because ultimately, the vivid memories are preserved within us rather than the photographs.
Though I won't deny that the fear of not capturing everything can get to me at times, thus I end up taking one too many snaps. I think that's a fear many people deal with when they take an inexplicable amount of photographs of the same thing!