I think everyone with an iPhone should be making every purchase they can with Apple Pay. I also think everyone who uses Apple Pay should open the Wallet app ahead of time, instead of simply tapping their iPhone to the card reader. But there's a much faster way to open Wallet than slogging through the sea of apps on your iPhone. You can open it right from the lock screen.
How? A good old fashioned double-click. If you have a Home button iPhone, quickly double-click the Home button. If you have a Face ID iPhone, double-click the Side button. When done correctly, your Wallet will pop right up on your lock screen, without you needing to unlock your iPhone.
Not working for you? You likely do not have a purchase card enabled in Wallet. Merely having a rewards card, like Starbucks, won't cut it. The shortcut will only work if you have a credit, debit, or Apple Pay Cash card linked. Bit of a bummer if you only want to use Wallet for rewards cards, but, again, I can't recommend Apple Pay enough.
Just updated your iPhone? See everything that's new with Apple's latest iOS update: