Why Duplicate?
So if the US military system is so great, why was it that no-one stopped the Iridium satellite from crashing into a piece of space rubbish? Because that wasn't their job. Their job was to look for intercontinental balistic missiles with nuclear warheads flying towards America.
So therefore a system that is designed just to prevent this type of thing happening, and is not affraid to publish the data of everything up there so that people can work out and avoid possible collisions is a good idea.
Redundancy is another reason. Why does your car have 2 breaking circuits? What a waste! We should get rid of one of them for you. Similarly when you fly on a plane, we should remove all the redundancy there too; it's so wasteful having 2 things that might do the same job...