Compared to UK plugs, the Australian pins are very thin and the earth pin is optional. This makes it easy to insert a plug at a slightly wrong angle and make electrical contact without the socket gripping the plug at all.

Also the pins can get bent out of alignment fairly easily, which almost never happens with UK plugs.

I'll agree the pins could have been made a bit thicker and they do bend a bit, say, if you step on them with shoes. But the earth pin is definitely not optional - it is not present if a device is double insulated, but must be present if the device is not (even though the live and neutral pins are angled so you can't plug it in upside down, and the neutral is grounded in the switch box - you still have the separate protective earth pin on the cable to every device that needs it in case the wall socket is wired incorrectly).

I'm not sure what you mean about plugging it at a slightly wrong angle, I haven't experienced that (in ~25 years of using Australia plugs).

If the earth pin is not optional, how do you plug something in if it isn't present? Do you have special sockets for devices that are double insulated?

I mean not optional by certification and law, not physically, so no, we don’t have different sockets - all sockets have earth, but it doesn’t have a shuttering system like the UK’s.

A two pin plug still plugs into a regular socket, it’s just illegal to produce or sell something without an earth pin if it doesn’t meet safety standards for double insulation.

Two issues I have seen with the AU/NZ standards:

1. When they introduced the plastic sleeve on phase and neutral pins, it severely weakened the pins of the plug and they can rip off inside the socket. Very very unsafe.

2. The standards are very weak on cheap four way plugboards - the sockets fail over time and have a variety of failure modes, especially fire risk. Buy quality plugboards (although hard to judge as a consumer).