The reasoning the people who take those give is that they're so much stronger than the natural ones that it's worth it. From what I remember, something like 1000x as strong.

Also, humans did not evolve with most of the food we eat today. We evolved in Africa, we didn't evolve to eat 99% of the fruits and vegetables that we eat today, we evolved to eat the fruits and vegetables of Africa. So I think it's a mistake to say we evolved to eat natural foods in general, we only evolved to eat specific natural foods.