Rwy 09 Usage - If this runway is requested by an aircraft during another Runway mode (eg Rwy 16 only), this is the process that occurs. The ground controller who takes the request assesses their ground traffic and whether they can process the aircraft on the ground through to the holding point.
If they can they then pass the request to the coordinator in the tower who assesses the overall traffic picture and asks the aerodrome controller (tower frequency) whether they can accept it.
The aerodrome controller assesses their traffic picture and makes a decision. If they decide yes, then the coordinator calls down to departures or approach to ask them if it's ok, the departures controller then has to coordinate with Essendon tower as a 09 departure abbutts the airspace that they own during Rwy 16 only operations.
Before the aircraft can actually get airborne off the non duty Runway 09, the tower controller must again contact departures controller to get instructions. All of this is additional workload and all is taken into account when assessing requests.
At any stage during this entire process, any of the above controllers can say "not available" and do not need to pass a reason to the controller requesting it. It is up to each individual controller to manage their own traffic levels and what they deem acceptable is different between different people and the traffic circumstances on the day. No debate is entered into as we do not have time to debate the merits of the decisions of other controllers and manage traffic at the same time.
Difficulties getting aircraft across Runway 16 are a valid reason for the ground controller to decide it's not available (it is not the same as a 27 arrival crossing after landing becuase on Rwy 16 Only there are arrivals and departures using that runway versus 27/34 LAHSO, mostly landing only using Rwy 34 and 27/34 departures north east, it's mostly departures only using Rwy 34, so the gaps for getting across Rwy 16 are smaller and less frequent.
The above coordination is done for any "off mode" runway request, and we don't say not available just for fun. Requests are always judged on their merits, but it does create extra workload for many controllers and increases the risk, which we are encouraged to minimise.
I'm not trying to make excuses and i can understand that it looks like the runway should be used a lot more, but just trying to put in context the process that needs to occur.