Placing the burden of fraud on merchants does make sense, as they are the ones present at the time of the transaction, and theoretically in the best position to

Placing the burden of fraud on merchants does make sense, as they are the ones present at the time of the transaction, and theoretically in the best position to authenticate the purchaser, via ID, etc. If a merchant is doing a bad job at it, and their prices go up, then consumers go elsewhere for those goods, incentivizing the merchant to prevent fraud. It seems to work well enough most of the time via market forces instead of needing government regulation and enforcement.