First, the airlines started charging for checked bags (remember when the first TWO bags were free?!)
Then, everyone started carrying their bags onboard and stowing them in the overhead compartment.
Then some of the low-cost carriers started charging for carry-ons, even MORE than the cost of a checked bag, to discourage carry-ons. It slowed down the boarding process, after all.
We all got used to the “lowest” fare and the associated “non-refundability.” The one day, we noticed there was one even lower fare, ah, but there’s the rub… no carry-on bag allowed; you had to check your bag (and pay for it), and no advance seat assignments were permitted.
The latest I’ve heard from a client is that the major airlines are now checking the weight of your carry-on bags, and when they are over a certain weight, they must be checked, regardless of whether or not they meet the size requirement.
To quote this client, “Emily, things keep changing.”