Why juice a vegetable and then dry it again?
It sounds like an odd extra step — juice a carrot, then dry the juice back down to a powder. The point isn't convenience for its own sake, it's consistency. A fresh juice starts losing nutritional value within hours, and not everyone has a juicer, the time to clean one daily, or a way to carry fresh juice to work.
Drying the juice at low temperature keeps most of what juicing captured, in a form that keeps for months, travels in a bag, and mixes in ten seconds. It's a trade-off, not a replacement for eating vegetables — most people who use these powders treat them as a daily top-up alongside meals, not instead of them.