I'd note that many people in my social circle and family forget that iron is a basic nutrient. It happens. People forget that sodium is as well, especially with all of the talk about how bad salt is for you.
Presumably the Soylent guy ought to be held to a higher standard of knowing what "basic nutrients" are, as he actively promotes himself as an expert on the topic and encourages people to buy his drink full of "all basic nutrients." If your friends and family aren't doing that, their ignorance is excusable.