[Someone1234]

They're scared that it might become popular and cost them too much.

The airline's business model is to try to charge people from point to point, this scheme takes advantage of that fact to find savings.

The airlines could, instead, change how they charge (e.g. per land mile/per minute in the air) but then it becomes harder to justify why direct flights that are cheaper for the airline to run cost consumers more, not less. And why inefficient indirect flights cost consumers less in spite of being more expensive for the airlines.

Airlines need to keep their current business model to prop up their hubs, but they need hubs due to their current business model. If you invented airlines today (particularly with the new Airbus and Boeing aircraft coming on-tap with greater range) you'd see far fewer hubs, and more direct point to point flights.

This is airlines trying to slow the inevitable, which is that they need to evolve.