The Florida orange growers invented the nonsense that a glass of sugar water, err, orange juice, was a healthy way to start the day at breakfast, to go with your bowl of sugared cereal. They did this when California oranges started to appear in stores, which have a better appearance, fewer blemishes, etc. So they needed to find another way to market their less attractive produce.
Of course oranges and other fruit have been bred over centuries to have much higher sugar content than the original wild/native varieties that people may have eaten (in small quantities). The term "nature's sugar" is sort of accurate, but not in a good way.