Apple Pay has finally caught on in the US, but one year on in China and it is still struggling.
Source: One year on, Apple Pay finding little traction in the Middle Kingdom
I think one aspect that is not mentioned in the article is that UnionPay insist that a PIN is entered when using Apple Pay (and in some circumstances a signature is required). This means that using Apple Pay is not really any different to using your debit or credit card.
The competition such as Alipay and Tenpay simply require the QR code to be scanned and the payment is immediate, a much better experience in my opinion.
It would not surprise me if this situation was intentional to ensure the business and profits stay in China.