LOL so almost 104 years later you could ask a silly question. Honestly I have no idea why, It just is a tradition. If you really want some info you could look it up, Time Square Ball.
I wikied this
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The first New Year's Eve celebration in the area was held in 1904. The New York Times newspaper had opened their new headquarters on Longacre Square (the city's second tallest building), and persuaded the city to rename the triangular "square" surrounding it for the newspaper. The newspaper's owner, Adolph Ochs, decided to celebrate the move with a midnight fireworks show on the building for New Year's Eve. Close to 200,000 attended the event, displacing celebrations held at Trinity Church.[3] However, Adolph wanted a bigger spectacular at the building to draw more attention to the square — in 1907, the paper's chief electrician Walter F. Palmer constructed a lit ball that would be lowered from a flagpole at One Times Square. It was constructed with iron and wood, was lit with one hundred 25-watt bulbs, weighed 700 pounds (320 kg) and measured 5 feet (1.5 m) in diameter. At first, it dropped 1 second after midnight. Even after the Times moved its headquarters to 229 W. 43rd St., the celebration continued.[3]
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