And another thing.
Pilots don't focus on it, but planners do.
For QF ( and it is not confined to QF) slot constraints are an issue at ports such as SYD, NRT, LHR because of finite constraints, and at ports like LAX and FRA, because of time of day issues relating to onward connections.
SYD is limited by runway movements for crucial hours of the day. Only way to move more pax at the most popular times is to increase the number of seats per slot. Domestically, that is 737-800 in lieu of -400, or 767/A330 in lieu of 737. A380 does the same versus 747.
All part of the mix.