Why do it? While I do not recommend that the cable crossover ever be the “cornerstone” of any pec-pumping-program, I do feel it is certainly valuable to include. Pressing movements are awesome for handling max poundages, while flyes, as mentioned earlier, are wonderful for their ability to stretch the pecs. However, neither of them provide a strong “peak contraction” effect, which can act as another strong stimulus for growth.
Tips: Some people try to use too much weight on this movement and turn it into some kind of standing press. Do not be one of them. Use moderate weights in good form, shooting for 10-15 reps per set. If your gym has a multi-angle cable station try doing this exercise from different points to stimulate unique sets of muscle fibers. Use the cable crossover for what it is truly good for and squeeze hard on every rep.