Maybe the army feel that if they had the tactical fixed-wing transports (which spend a fair amount of time transporting or inserting army personnel) they might actually get to experience the novelty to have:
1. the Herc actually turn up to fly the grunts around and
2. the pilots not "run out of duty hours" just about beer o'clock.
What does the RAAF need heloes for? The mud-moving Hornets should be next so the army can make sure the Mk82s land exactly where they are meant to and on time.