Same reason there's a scale model of a landscape in the middle of China.
They even shrunk their army down to exercise on it:
Ok, so maybe they didn't, but the landscape is real, you can see it on Google Earth.
Chances are that the carrier will be the target of a new weapon that Iran has in development, probably a missile of some sort. Heck, maybe they'll nuke it with the nuclear bomb that everyone has said that they've been on the verge of getting for the past ten years.
