Do you think William would have gone if it hadn't had been so far away?
I think it's somewhat of a moot point now, but I'd say there's decent odds he would. If it was within Europe or even North America it could be done (at a push for some areas) with a night away if they didn't commit to other events while there to add some PR.
Getting to Aus? On a commercial flight they were looking at around 23 hours flight time each way. So commit to two days purely to getting there and back.
Arrangement of either his usual team of folks (i.e. flights and accommodation) or an Aussie team would need some wrangling, and if flying out English staff you're going to need to add a bit of time padding for simple avoidance of cruelty. Expecting someone to go from 23 hours of travelling straight into work mode with about a 10 hour time difference is not a working condition staff are going to withstand well.
I think people are just going "oh, a first class flight and a football match? Suck it up and do your job" without thinking of all the moving parts and other, non-royal humans they might be committing to that travel and turnaround with little to no notice.
I am a little biased as I
have had to do the trip of NZ to the UK on short notice, and I'd not sign someone up for that exhaustion solely to see them get a bit of press.