Some of these terminals are oddly designed. Often the screen says "tap to pay," but you tap something above it that's not clearly marked, not the screen. Enough of the others have you tap the screen that you think it's that. Or a part says "Apple Pay," but that's just advertising the feature, and there's some unmarked area to tap.
But even for the ones that are decent, idk why I'd not just use my credit card.