Be honest - think back to when you were 16. Did you have an understanding of a broad range of issues? Did you pay serious attention to national news? Okay, even many adults may lapse on the score, but still, it seems crazy to me.
In the U.S., voting age had been 21 and the only reason it was lowered to 18 was that teens were being drafted to fight in Vietnam, and it was felt as unfair for them to have no say.