tusitala,
Perhaps It's cause they don't have a 'conversion course' fit for delivery; or simply they are unable to find an egg in the hen house.
They seem to be able to bring RAAFies across to the civil side, don't think it would be too much trouble to bring across FNs.
Also it may be jsut because it would need a brave manager to bring in newbies when the current philosophy is reduce, re-use, recycle; in that order...