Marketing. Initially based around the idea of replacing all food with it (which even the founder stopped doing during his initial trial).

It's tapping into a lot of sentiments around food as a "problem" or "nuisance", where a lot of the other shakes on the market have gone for the health and fitness angle, or the "I'm too important and busy to sit down and have breakfeast so I'll down a shake on the go" angle.

But it's not bringing much more than marketing.