Boots can contact each other without much harm, but ski edge contact can ruin them. The ski waist only hits the snow briefly when landing a jump-turn. LESS side-cut aids in longer radius turns. One skier wants less side-cut to bomb the run with stability and confidence. A less aggressive skier also wants less side-cut for a relaxing, easy cruise.
Mogul skiers prefer less side-cut so the skis go where they are pointed.
Powder skiers want less side-cut for even different reasons. Extra side-cut has less effect in powder, and takes away float. A skier who leaves the snow, with jump-turn style telemark skiing also has less need for sidecut, relying on balance to throw the skis into each stance. Choosing side-cut measurements on your new ski is difficult, because you re obviously going to turn all of these ways and in all of these conditions. Choose a ski by either what you enjoy the most, or what you need for a specific task.