Why does my invoice not display currency

I know that America is the centre of the earth, and the worlds No. 1 everything, however when you are dealing internationally to countries outside the USA (yes there are!) like Apple does, how about you include the currency on the invoice. I have brought a number of different Apps and other items and the bill always shows dollars however we have dollars as well.

PS They are far more attractive and colourful as well! OK, not worth as much I know...