The less bandwidth and paying more are only due to stupid pricing models from the infrastructure provider (NBN), for anybody who isn't familiar with the system. There's no technical reason for it in 60% of the country. They could upgrade anybody in the FTTP footprint to gigabit this afternoon and anybody in the HFC footprint to at least 250 or 300Mbps but are limiting everybody mostly to 100Mbps (but most people are on lower speeds) just because they want to gouge providers for bandwidth. The artificial limitations created by these pricing models also mean that a lot of providers skimp on buying the necessary bandwidth, so for most providers (there are only a few good ones) there are unnecessary slow-downs at peak times as the artificially limited bandwidth gets congested. It's madness!

The rest is unfortunately served by satellite, FTTN or FTTC that aren't able to deliver the speeds, or for the fixed wireless footprint it is also limited, but to a large degree only because the LNP government shelved the planned backhaul upgrades to save some money, so there are all these wireless towers that are served by low-speed microwave backhaul. The plan had been to upgrade any tower to fibre backhaul once the microwave backhaul reached a certain level of utilisation, before it was fully congested. That now doesn't happen, so those users just have to deal with speeds dropping significantly at peak times.