Yes, it is. A lot of people don't like cooking, they don't know quantities, they don't necessarily want to eat the same things again, and they're used to their eating routines.
Take the typical 9-5 person. They wake up, probably have a very light breakfast before work, eat at noon, maybe a snack late afternoon, then go to the gym...workout...have dinner...it's probably around 8-9 by then. They're not going to have another full meal.
Heck, for some, they even skip breakfast. Eating 3 full meals is a challenge for some, let alone add another one or more.
You also assume people are happy just eating more ground beef and rice. A lot of them aren't.
Telling them to drink this thing, which takes about 30 sec to prepare, and maybe a minute or two to drink...it's a lot simpler to them.
I love to eat, and I am lucky enough where I could pretty much eat as many times I want during the day, but I know that's not everyone's reality.