I love using Apple Pay but I'm frustrated that it's just not accepted at very many places--three years after Tim Cook introduced it (at the iPhone 6 event in Sept 2014).
McDonalds, Walgreens, Best Buy, Panera, Trader Joes, plus a handful of other stores I rarely if ever visit. Most of the stores on Apple's "where to use apple pay" list are not located in my area.
Walmart has rejected Apple Pay in favor of its own system, probably to avoid giving Apple a sliver of its gigantic profits. (Apple gets 15/100 of 1% from each Apple Pay transaction, or 15 cents out of every $100.) Other stores have their own contactless pay using their own app - like Starbucks (which also accepts Apple Pay, apparently).
Because contactless pay is fragmented, and not that much more convenient than paying with a credit card, adoption is slow.
If there were a single standard for contactless pay, stores would have more incentive to adopt it, consumers more incentive to use it.
Among single standards, I like Apple's approach. It seems more secure than others (please correct me if I'm wrong here!). Using Apple Pay is super quick--you don't have to open a store's app and then navigate to the app's bar code screen. Apple's fingerprint sensors since the iPhone 6S have been very fast. FaceID is reportedly very fast.
But I don't think there's much chance of a single standard emerging. Google and Apple would have to agree on using compatible technology, which doesn't seem likely. And Apple would have to give up the .15% it earns from Apple Pay transactions in order to make Walmart and others give up their own contactless payment systems in favor of the new standard.
So the best we can hope for is that Apple Pay continues its unfortunately sluggish growth in market penetration.