While this is true, cash or cash equivalents, such as an IC card, can in many cases be more convenient or universally accepted. Since I don't have an iPhone (or Japanese Android phone), I don't have a Suica card in a digital wallet with digital wallet top ups. For that, I top up my physical Suica card with cash from a 7-Eleven ATM, which does have DCC.

In keeping with the topic of this thread, I will also use cash for small transactions in places where forced DCC is ubiquitous. Some countries make it difficult, if not impossible, to opt out of DCC. While I might be inclined to fight a bunch of < US$5 charges with forced DCC on principle, I recognize that a card issuer in the US is more likely to simply issue a credit for a currency transaction dispute rather than pursuing a full chargeback with the merchant. In those cases, the merchant gets away with DCC on the transaction even if I as the customer am made whole.