I've never been asked to show my ASIC at YMMB. Most of the time I just leave in the plane anyway.
Years ago the LAMEs mentioned that Federal Police (?) would do the rounds checking ASICs, but I hadn't heard of this recently.
I think the reality is that, unless you paint an Islamic State flag on the side of your plane, you could pop in and out of Moorabbin without a current ASIC and noone would know or care.