Because China cannot force anyone to buy their airplanes, or any product for that matter. I can tell from your tone that you are hostile to the West. But I can also tell that you know little about aviation so am going to be nice in response to you.
For the airplane, there is the certification process involved. Certification means standards. It means that the rest of the world is uncertain about Chinese designed/built airplanes. There is nothing wrong with this. Before the USAF, I learned how to fly in a Cessna 152. If Cessna have a newer version of this venerable little airplane, it still must go thru the same certification process as anything Boeing or Airbus or Bombardier produce. For passengers, essentially the most precious of all cargo, the Western countries have a history in aviation literally from the start of aviation. China does not. It means the standards today came from Western aviation, not China. That does not mean Chinese aviation will not succeed. I said 'will not', not 'cannot'. Technically speaking, there is no barrier for China, but trust take time and this is where the 'will not' come in. China proved they CAN design and build a functional airplane. Now it will take time before the 'will not trust' turns into 'will trust'. And no one can force that time.
