Why are contactless cards called contactless if tapping is required?

They are called contactless because there is no physical contact being made to read the data off the card (like a chip reader or a magnetic stripe reader).

Contactless cards utilize RFID / NFC (Radio Frequency Identification / Near Field Communication). There is no ‘tapping’ required. You just have to bring the card in close proximity for the card to be illuminated by the antenna in the POS terminal.

As a matter of practice, it is easier to just tap and place the card rather than holding the card 1 cm/inch away from the reader.