Absolutely necessary in any training program. The beauty with using cables, is that you keep continuous tension on the muscle being worked, both in the positive & negative phase. Due to a bicep tendon displacement, I have been using cables heavily in my arm workout. There are many variations of the curl that you can employ. Close grip, wide grip, reverse grip, standing close to the rack, standing away from the rack, between the legs, & thats just for biceps. Then theres forearm work , triceps etc. Dont let people tell you these exercises are just for finishing your arm workout. You can still use heavy weights & achieve muscle failure on cables & its much harder than using, say a barbell, if you get your form proper & take advantage of the continuous tension on the muscle.