The actual risk of a merchant not receiving money for a credit card transaction is quite high. Chargebacks are enough of a business problem that many large retailers have whole teams only devoted to processing and disputing them. There are entire companies that create products and services to help merchants reduce just "friendly fraud" chargebacks—that is, chargebacks where the cardholder says the purchase wasn't authorized but they are just lying or it was a family member who made the purchase. That there are entire industries devoted to helping reduce it shows that the risk of chargebacks is definitely something that merchants take into account in how they run their businesses.

In case of a stolen credit card, it's 100% the merchant who pays (that's why they're called charge-"backs"). The only exceptions are if the transactions are indemnified by a third party partner.

All the card brands have multiple chargeback codes for fraudulent transactions, even card-present ones, so the fact that the credit card was physically present is not some kind of guarantee that the merchant would win a chargeback representment.