TL;DR: producers store juice in oxygen-less tanks, for up to one year, then add natural/synthetic chemicals, to restore taste, prior to distribution. The author suggests people make their own juice, instead.
If you want fruit, eat fruit. If you want a drink, drink some water. Why combine the two?
Fruit juice seems like basically a way to drink soda but with the delusion that it's good for you.
Sure, the stuff tastes OK, but not as good as the fruit it comes from.
1) People know what's good for them
2) People want what's good for them
The existence of an economically viable product such as juice indicates that whatever the industry is doing, people want in its presented form.
Whether it's good for them or not is a completely different question.