The condition of microcausality (commuting fields for spatially separated points) can be shown to hold in the Fock representation in quantum field theory (see e.g. Peskin & Schroeder section 2.4). However, in algebraic quantum field theory the condition of microcausality is postulated as an axiom (Haag-Kastler axioms). I had expected that a theory of observables that is defined in Minwkowski space-time should inherit naturally the causal structure of special relativity, and, therefore, microcausality should be a derivable result, but not an axiom. The fact that the Fock representation makes it possible to derive microcausality seems to be irrelevant (or of no generality) in algebraic quantum field theory due to the fact that there exist inequivalent representations of the algebra of observables. Is this picture correct? If yes, why is there a need to postulate microcausality in AQFT in contrast to the usual Fock representation in QFT?