It’s not of both; significance of contactless technology that are used in Tap to [__] is that they require neither electrical nor physical connections. There are other RF-based technologies that require no conductive surfaces but some sort of mechanical touches.

The reason why the users are instructed to slam the card or device is because users fail to perform required actions if simply told to hold the card or phones just right. Spatial cognition isn’t a forte for many.

The reason why tap is used in VISA contactless over touch is probably because Suica system used by JR East uses the phrase “Suica is touch 1-second”.