lower crew requirements
is actually a big issue for Oz. for some reason, humans dont like 4 months plus away from sunlight, let alone family, pubs and friends. Pay not keeping up with CEOs and senior clerks in suits also does not help. The unreliability of the Collins class means submarining is not seen as a career as you get so little sea time anyway while the latest bug/stuffup/great idea in gold plating is fixed/repaired/added/mangled.