And to be fair to SYD they (SYD Airports) do provide such a servce via the T Bus. The big problem is that they are not frequent enough and/or inconsistent.
Probably half the reason QF set up their transfer in the first place (and IIRC VA had one at some point? or maybe AN did. I don't recall)... because the provided services weren't good enough and this was a premium service to get you through security and into the domestic terminal in a timely fashion. You know because as a premium legacy airline this is the kind of thing they do.
Now in BNE you get directed to their bus, as with PER but I suppose these are smaller stations so the cost to set up a dedicated service was probably just not going to work but SYD is another issue.
I do agree though most airports in the world provide passenger transfer services between terminals.
though can anyone think of setups that are like BNE,PER and SYD where dedicated international and dom terminals are a significant distance away or in a configuration (unliike, for exaple, LAX) where either a airside or direct access solution is not available? There must be some, but offhand I can't think of any. Even AKL one can walk between dom and int (and there's a bus too IIRC). HNL has the intra island terminal, but it's easily accessible iirc. CDG, which is a crazy place still has inter-terminal transfers. LHR of course has both airside, and landside transfers (coughbersome if coming into say T2 and going to say T5 landside) but they are there.
I suppose places like Tokyo and Moscow where (traditionally at least) international and domestic services had entire airports (remember when HND was domestic only, and there's ITM if that is still going?), or BKK where the old Dom Muang was transformed into a domestic only airport.. so that is a totally separate situation but most places are far more integrated.
You'd think it would be more efficient for the airport operator to provide these services without the airlines being involved. Problem is when they're not quite good enough....