Most parts suppliers to safety-critical products have been in business for a while and have established a culture and internal checks-and-balances to ensure quality. It takes time to build up such a reputation and known-how to demonstrate to customers that their internal processes ensure quality. You can't just claim it's "good", you have to show it's good from start to finish. Reputation is hard to gain and easy to lose.

China's industry is relatively new, and may not yet have gotten to this stage yet.