Why Is Our Money Copyrighted?

I was looking at a bill the other day, and I noticed the following very small text at the bottom of a $10 bill: ©2005 BANK OF CANADA.

Why on earth do we need a copyright notice on our money? After all, it's a banknote and there is already a whole regime of law devoted to punishing those who make illegal copies of it. What possible benefit does a copyright notice convey? Perhaps its a little joke.

So, if I were to make some counterfeit money, would I be charged with copyright violation in addition to the funny-money crime? Maybe they're copyrighting the artwork and images on the money. But why? It's not like the Bank of Canada is a commercial interest that makes money (so to speak) from these images, so why do they need copyright protection?

I'm just curious, that's all.