We don't need to, but it does help the taste. I need to drink my salty water, but it tastes kinda weird. Sugar, and very limited amount, makes it taste like gatorade with much less the calories, since gatorade is trying way too hard to mask its taste. And depending on where you are and your dietary restrictions, someone may not get all they need naturally. Depends on what's available to the person. The inner city is very sparse when it comes to fruit, and so people have to get their fruit nutrients elsewhere there.