Money persuades barely half a cabin, and less reliably than simply being offered a better seat, which only makes sense once you know the seat is now a purchased object rather than an allocation. Airlines began charging for seat selection in the mid-to-late 2000s as pure ancillary revenue: putting one passenger in 14A rather than 31B costs the airline essentially nothing, so the fee is close to free margin. It became very large money. In 2022 eight US carriers (Alaska, Allegiant, American, Delta, Frontier, JetBlue, Spirit and United) took $4.2 billion in seat charges between them, with 2023 prices averaging about $33 for a preferred seat, $48 for an exit row and $18 for the last row; low-cost carriers would be largely unprofitable without ancillaries of this kind. Once a passenger has paid for a specific seat, a stranger asking to swap is no longer making a request about courtesy. They are asking someone to hand over something they bought, usually for something worse, and sometimes for cash that does not cover what it cost. That is why the offer lands badly even on people who would have moved for free.