Funny Money

This is just a slight complaint.  Something somebody should have asked me about first.  Before they made it the NATIONAL MONEY of Australia.

Below, in a terribly out of focus photo, you will see, from left to right, the American Dime, the Australian five cent piece, the Australian 2 DOLLAR coin, and then the American Nickel.  Now, why is the 2 DOLLAR coin so small?  So people will lose it and then other people will find it and then be super happy? 

Now, spend a month in Australia, and get used to the tiny 2 dollar coin and the larger 1 dollar coin.  Proceed onto New Zealand where their money is the EXACT opposite.  Below, on the top row, we see a New Zealand one dollar coin, smaller as it's supposed to be then the larger 2 dollar coin.

Bottom row: Australian 50 cent piece, which is HUGE, then the Australian one dollar coin, and lastly the Australian 2 dollar coin.  Can anybody make sense of this for me?

(**Interesting to note that the Australian 50 cent piece still has a picture of Lady Di and the Prince of Wales on it.) 

On my first day in Australia, I bought something for $5.80, (let's say...) and gave the woman a $10 bill.  She handed me a handfull of coins.  I need my change, I say.  You've got it, she says.  Oh, you gave me just the change, I need the bills, I say.  Then she explains that I have all the change.  Of course I was hugely embarrassed, and thus began a month of carrying around six pounds of coins in my purse.  Not realizing of course that there's like $50 in there.