Apple recommends six specific payment platforms to use with ApplePay
Apple tells developers, "You can find a list of payment providers who support Apple Pay with their SDKs on developer.apple.com/apple-pay/. Using one of these SDKs is highly recommended." These six are: Authorize.Net, Chase Paymentech, CyberSource, First Data, Stripe and TSYS. As notable as inclusion are those who are absent.
Source: http://www.pymnts.com/news/2014/apple-pay-recommends-six-processors-and-paypals-not-one-of-them/
Related: https://news.ycombinator.com/item?id=8330629 I have to imagine this is because the Apple Pay system directly integrates with (admittedly outdated) tech such as 3D Secure, Visa and Mastercard forms of tokenization, and the incumbents other systems. These are traditionally very different from a new technology such as PayPal which, IMO, doesn't seem to be a standard gateway at all.