Why Aliens Haven't Contacted Us Till Now?

Because extinction of intelligent life is so common throughout the universe that before an intelligent civilization could become advance enough to develop a technology to make contact with other intelligent civilization, they go extinct. Don't believe me? Here's some news for you. In 2008, an informal survey of experts on global catastrophic risks at the Global Catastrophic Risk Conference at the University Of Oxford suggested a 19% chance of human extinction by the year 2100.