I think that view is overly generous. On flights where free check in luggage is offered there’s plenty of room for carry ons in the cabin, so a good amount of p

I think that view is overly generous. On flights where free check in luggage is offered there’s plenty of room for carry ons in the cabin, so a good amount of people clearly opt for check in when it is free. When they started charging for check in is when it became the norm that people where then pushed to gate check their carry ons for free once space was getting full. People were shifting their behavior to avoid the fee. The result, not surprisingly, is that fee avoidance is too common so the airlines make it more difficult to do so. It is, of course, a “hidden” price hike with the advantage that your flight remains ranked higher when sorting by price.