Comment by swiftcoder

4 hours ago

> the merchant can unilaterally decide not to use it

If they do so, they are telling the card issuer that they are happy to be on the hook for chargebacks/fraud. It's not an decision without consequences

Comparing to fraud 3DS reduces sales turn over by a lot, and this is the reason why for the most part it is not required in the US, too much friction during check out hurts business.