Jealousy and fear. PayPal is jealous and afraid. Otherwise, there would be no reason to pre-emptively attack Apple Pay.
But I've used PayPal on occasion. It's OK, but mostly because a few online stores use it as the preferred method of payment (ahem, eBay). Otherwise, I wouldn't even be using PayPal whatsoever.
Once Apple Pay gains the ability to pay online transactions (rather than just the NFC chip on mobile phones), then bye-bye PayPal.
With huge banks and credit companies (MasterCard, VISA, Amex) already supporting Apple Pay
. PayPal should be very concerned about its future.