Rotational movements are very rarely isolation exercises.  They are composite (involving more than one muscle or muscle group) and mutli-faceted movements that challenge not only physical strength and power, but also stability, co-ordination, balance and flexibility.  Having to actually move your focus during a movement primarily takes away the stability of a movement and requires you to activate and stabilise in areas that are not directly related to the movement itself, but are vital for any action that takes place in the street or certainly on the sporting field.