Because what we call "lemonade" in Europe is not the same drink as what is called "lemonade" in the US, although we usually have our own variation (citronnade in France) that corresponds to the American one.
Where did this bullshit come from? Sprite is not lemonade in Europe or Australia, it's lemon and lime and I don't know anyone who doesn't know that.
There's loads of brands of lemonade here and Australia, cloudy, traditional, clear...wtf?