It's good we have something better. 

 They may be worthless, of limited worth, but they're not useless. They're still accepted everywhere for virtually every transaction, making them useful. That's different from value.  

 You are right that I was talking about value but if you want to get all in to the weeds they Aussie dollars are used far less as well as measured by either population using them or GDP. 

 Less compared to what other instrument?  

 Less compared to eachother. We are talking about Canidian vs Aussie dollars. 

 Oh, I thought you were talking about value related to some other instrument.