I am at the Revolut event now. Arthur Johanet has just announced that Apple Pay will be coming soon. They will be launching in the UK first in early June followed by the remaining countries (not the whole EEA) in late June.
The excuse he gave for taking so long is that they’re working with two schemes - MasterCard and Visa, as well as multiple card designs. Just like other card issuers.
They’re going to do in-app provisioning, just like American Express UK launched today. But the impressive part is instant issuing, so you won’t need to wait for a physical card to arrive to start using it with Apple Pay. It will also be available for virtual cards.