I often like to crop as I go through and do my ratings (sometimes on first pass i.e. 1 star, usually on second pass). Since I can't use the mouse scroll wheel in develop module, and it's slower to load the images in the develop module, I go through my images in library module. hit r to crop then go back to library but the round trip is kind of a pain. It'd be smoother to let me crop in library mode.