Why would online retail not also be a match? I assume there is are many more online retail transactions than travel related transactions simply because people shop retail more than they travel.
People did not shop online that much, 15 years ago (especially outside USA). But they already had travel booking needs, which could be taken fully online with CC payments over the net.
You could often pay upon delivery even when shopping online, but there's no need of delivery for tickets.
A web site which offers payment-upon-delivery goods is a glorified mail order, anyway. It does not transform the experience much apart from removing some friction.
