> Because the "security model" of credit cards involves shifting all seller-fraud risk onto the sellers using chargebacks.

This is actually one of the two primary services that credit cards sell themselves on -- mitigating risk, primarily by protecting consumers from fraud, and permitting purchases on credit rather than out of available cash balances -- and its the feature that is most heavily sold to higher-end customers (the you can buy stuff you can't otherwise afford feature is sold more heavily, at least more equally to risk mitigation, to lower-end customers.)