Checked bag fees have gone up and become pretty outrageous as ticket prices (airline and route dependent) are already high. Passengers have figured out that gat

Checked bag fees have gone up and become pretty outrageous as ticket prices (airline and route dependent) are already high. Passengers have figured out that gate checking a bag is free so more people showed up with a carry-on and counted on gate checking. Then they realized that it's faster if you don't gate check because you can just grab your bag and leave the airport. Now, more and more people are showing up with bags they don't want to check, but the overhead bins are not able to store a full-sized carry-on bag for every passenger. If people don't gate check enough bags, the flight gets delayed while people spend 20 minutes trying to fit their 10" wide bag into whatever 6" wide slots they can find, or you get the assholes that start pulling other people's bags down (I've had to stop a few people from doing this to my own bags) to make room for theirs. Finally the bags get gate checked anyways. The aggressive push to get people to gate check is to prevent that last part, the delays. The airline makes no money on it (at least the non-budget carriers), but they lose money if flights are delayed and cascade into potential cancellations or delayed enough to trigger some kind of credit, reimbursement, or travel insurance coverage.