It seems like the answer to this and similar questions on here, which is Soylent's true "innovation" in my estimation, is that Soylent is the first meal replacement with young men as a target market. Meal replacements are pretty convenient, but if you're an 18-25 y.o. man I have a feeling there's a nonzero level of stigma (real or just feared) associated with drinking SlimFast ("women's drink") or Ensure ("old people drink") all the time. Before now all there was for young people were protein shakes + multivitamin, which is also possibly too associated with bodybuilding/gym rats for comfort for some people.

But if you're a young man drinking Soylent, this hip new VC-backed tech fuel drink, it occupies a similar mental association space to Red Bull. I can't help just seeing it as a marketing thing.