According to Europe, we all harmonised our power supplies at 230v, except we didn't, we just added tolerances either way (european power goes between 220v to 240v, so that was just a wasted exercise just to make up a law that had no meaning), so, because manufacturers have to work with such a wide range, they have to have their own tolerances too, so, they print a maximum power used rating with a voltage rating that usually says 220-240v AC...
And some people wonder why the UKIP party exists... :\