Earlier quoted context omitted.
Why 90 days ? Why juice ? And what's supposed to happen ?
Because 90 days is long enough to see results for most people, but not so long that it's an impossible time frame. Because drinking 10 lbs of vegetables is doable, but eating them is almost impossible raw. If you cook them, it's still hard to eat 10 lbs of vegetables and you've killed a lot of nutrients. Because it gives your body a break from digestion. You'll feel a lot better. Edit: even those that think the idea…
But you don't say why and how it's relevant to the topic at hand.
Anybody can come up with "eat vegetables". "Eat food. Not too much. Mostly plants."