[elastic_church]

its just arbitrage.

airlines sell a mile at an average of 1 cent, banks charge merchants 3.5 cents for every dollar.

consumers can win if they pay their credit card off on time. many of them are able to churn by putting business travel from their employer on their credit card and getting it reimbursed in time.

banks can win double and triple if consumers don't pay their credit card balance completely one time, just once.

since the credit card aspect was already there whether there were good loyalty programs in existence or not, its actually a decent ecosystem!