Apps like Aperture and Lightroom allow you to do `most of the edits'* much quicker than other combinations of apps. You can set the white balance in a sequence of photos within seconds, transfer other types of edits (crops, etc.) to other photos, sort, add metadata (e. g. some people use that to associate model releases to photos), find, organize, backup publish photos.
So the promise of Aperture and Lightroom is a sped-up workflow.
* What constitutes `most edits' is very different to different people. One way to think about it is this: you do all the edits to a photo until you can decide whether or not it's a photo that you want to work on for many minutes or hours with Photoshop.