Comment by raw_anon_1111

You are being “tracked” that you got on the plane regardless, even your credit card company gets your complete itinerary where you traveled from and to and can (and does) use that for advertising.

Amex even knows whether you used your card on Delta for instance to buy a ticket or pay ancillary fees/drinkd on board. They use the information to see whether you are eligible for a credit (Amex Platinum)