You are flying along (singing a cowboy song) at 1000' ago. How do you know you are in the circuit area of an unpublished airstrip? In the Sydney Basin the vast majority of radio traffic is on YSBK, YSCN or YSSY. The other allocated CTAF is YWBN but you wouldn't want to do a Mayday on that frequency because it is very quiet, especially on weekdays. There are a number of unmarked private strips but I wouldn't have a clue where they are. This proposal means that, for safety, one shouldn't fly below 1500' AGL since you will never, ever, know what is lurking below.