Not financially viable perhaps? Logistics of having international players flying in, having to quarantine, or of them deciding not to compete at all. Doubt golf is as desperate as the AFL to fulfill its contracts in a dangerous and complex climate.
They were rescheduled for Feb, I think, which clashes with the US tour and unlikely to even get the Aussies to come home. From what I can gather the organising bodies actually tried everything they could to play but just couldn't make it work. Unfortunate given the number of eyeballs on TV because of the virus.