Because facts won't answer every question, we're left to judge. Not all opinions are valid, of course. Sound opinions support themselves with clear judgments from reliable facts. Appeals connect arguments to audiences. An argument can appeal to readers' needs or values.
Values come from needs.
The extent to which we hold the value of honor important, for example, depends upon how much need we have for belonging to a particular group identity. And the very meaning of honor varies by context and culture. Past claims and support are assumptions, what Rottenberg and Toulmin call warrants.