People who use powdered food shakes etc. generally do eat other foods too. As for reasons why they include powdered foods in their diet, it is often as a tool

People who use powdered food shakes etc. generally do eat other foods too. As for reasons why they include powdered foods in their diet, it is often as a tool for losing weight (replacing other meals), or for bulking up (in addition to other meals), or as a lifestyle or economic choice (easy & cheap weekday breakfasts). If you believe a significant proportion of powdered food fans eat only this stuff, you are unwittingly participating in someone’s marketing ploy.