Originally Posted by
moondog
Why should buying points be considered a travel expense?
Because they're spent on travel.

Seriously, though, I get your point. Still, the whole category thing can be pretty loosey-goosey.
Card issuers use merchant category codes (MCCs) to classify purchases. But they have no control over which MCC a merchant receives, so that’s a factor to consider when looking at what purchases qualify for bonus rewards. --CNBC
.