Alternate fuel.
Back in the mid 70s, in the days of the "great Australian air race" Ansett 727 blew some tyres landing at Alice. TAA, as was usual were second. No requirement for alternate so no extra fuel. These were the days when DCA provided operational control and they advised the TAA 727 to divert to ISA. Captain refused saying while he could get there with absolute min reserve there was a PROB 30 of TS at ISA. Captain declared that runway available at Alice was adequate and he would land there. DCA relented but instructed him to land over the disabled Ansett 727. The TAA captain declined and said he would prefer to hit the obstacle at 10 knots rather than than 130 if the approach was misjudged. He landed towards the disabled aircraft.
Sometime later as an FO on 727 I submitted a fuel request for a flight from BNE to ISA carrying enough fuel for Alice. The captain berated me about the extra fuel all the way to ISA and on the ground made a point of asking a grounds man how long it would take to push a disabled aircraft off the runway. The Captain's complexion paled when he was told it would take at least 24 hrs to get equipment to the aerodrome to do the pushing.
Any Captain of of a jet in Australia who does not have the capability to divert from any of our single runway airports has not given much thought to his responsibility for his passengers.