I really don't see the point
I could see potential uses for people on extremely restricted diets, under the supervision of a dietician and providing the ingredients were rigorously controlled and medically efficacious. I suppose it might also prove useful in survival kits and suchlike, providing there were fresh water to mix it with. But those are edge cases for situations where there few other options.
Otherwise, these powders are bland, expensive and actually require as much or more preparation and inconvenience than just eating an energy bar, cup-a-soup, pot noodle, sandwich or whatever else constitutes actual food albeit of the convenience variety.
And preparing, cooking and eating food is a pleasure - the taste, texture, smell, variety, the feeling of a full belly. Anyone who is so time poor they can't eat real food, even fast food, is not addressing the fundamental problem by eating / drinking glop.