I suspect that long-term acolytes of Soylent are victims of marketing, rather than having made rational nutritional choices. Their product does seem to be targeted toward a particular psychological niche.
Soylent replaces pb&js, dominos and eating out. Continuing to attempt to overcome my inability to care enough to sink more time into nutrition is the irrational choice. A moving to a product with both a superior nutrition and effort profile seems pretty rational to me.
Few of my co-workers went partially or fully on it, and they all look less healthy. But that's just a small random sample. Idk, who am I to tell them what to eat and that they actually need way more finer to dodge potential colon cancer/other nasty stuff.
God forbid if people were allowed to make their own choices.