cause ford does very few things that make sense. probably when your car was built, the people assembling the right used one kind and the people on the left had another kind. you see this a lot on cars.
The rivets are different to adjust the Camber setting to within specs, altough there isn't much adjustment it can be tweeked a little. All the loose Ford tolerances that are stacked up from side to side will often create the situation you have. Before I put CC plates on mine they were the same as yours.