Any airforce’s CORE business is operating and maintaining air assets airborne (all logistics, expertise, and operations are tailored for this purpose). Any Army’s CORE business is Infantry, Cavalry and Artillery.... Especially in smaller defense forces (which the Australians are as well, airborne personnel and assets are a niche asset within the Army and therefore do not necessarily become the attention/handling/budget/mindset it requires to properly operate these airborne assets. It is in that case way easier to integrate an already smooth operating Air Force unit with an Army or Navy operation.