The long story / technical explanation is:

Verified by Visa / MasterCard SecureCode put the burden of proof in a fraud situation on the cardholder that's why most merchants are way more relaxed. Bangkok Airways and CX never asked me to show plastic when I check in on a flight that was booked with successful Verified by Visa authentication. The risk for the merchant is low. The cardholder cannot charge back.

With traditional online transactions the merchants are very careful because it is up to the merchant to prove that the transaction was legit. The cardholder in most countries can cause a chargeback by simply calling the card issuer and saying "it wasn't me".

With a VfV or SecureCode transaction you would have to prove that you didn't make the transaction before a chargeback could be considered. That's why the merchants love it and that's why you can book tickets for other people and they can just go to the airport and show up. No card present. Cardholder not present. Your IP address doesn't match your billing address, card holder and ticketed pax are different family names, all possible, no worries ^