It is not a need but if you value convenience it is a card that you should have. It’s a prepaid smartcard that uses contactless technology, making your daily transactions easier with just a tap. TnG cards are used as a mode of payment for highways, public transport, selected parking locations, retail and also theme parks. Here's an article if you need further details

https://www.motorist.sg/article/290/a-singaporean-s-guide-to-the-malaysia-touch-n-go-card-and-system