  Ought implies can, but is it humanly possible to maximize expected utility?  March and Simon (1958) point out that in order to compute expected utilities, an agent needs a dauntingly complex understanding of the available acts, the possible outcomes, and the values of those outcomes, and that choosing the best act is much more demanding than choosing an act that is merely good enough.  Similar points appear in Lindblom (1959), Feldman (2006), and Smith (2010).