the abdominals are stability muscles. that is what they do....when you squat, when you deadlift, when you press things over head (and not do fucking gay lateral raises), your abdominals contract to form a girdle and stabalize the spine.
who the fuck cares if you do crunches or not.....for many people, ab exercises could be a bad idea because they cause excessive amounts of spinal flexion, exposing the disks.
that is why i say the best ab exercises are stability exericses like planks or bird dogs, etc......doing them for extended periods of time (since the deep stabalizers of the spine and postural muscles are predominantly type I fibers). Then take that stability and transfer it to a skill like deadlifting or squatting where your abdominals will gain lots of strength.