Flown SYD-PER return and was told both sides that QF doesn't provide the plastic bag for prams. There used to be a help yourself pile of bags at SYD which has been removed. Another service enhancement?
I flew recently (BNE) and near oversized baggage drop off (where I have to drop the pram and sometimes car seat) - they had a self help roll of large clear plastic bags - I go there and secure the items and then check in - will be disappointed if they have been removed
BNE always want the plastic bag when checkin in with other luggage (and then deposit at oversized baggage), most other airports not interested in a bag, and some let you just put it on the conveyor belt with the rest of your luggage.
There's also huge variability in which QF ports you can gate-check the collapsible stroller and which ones you can't.
Virgin are far more consistent in gate-checking being allowed (almost everywhere IME).