Unfortunately a path to the future, sorry to say. Many airlines are finding that the 'carry-on bag' allowance, as opposed to the checked bag, is being abused by passengers. I have seen pax trying to stuff obviously oversized/over-weight bags into overhead lockers. All this could be avoided if greedy/cheapskate pax played by the rules for carry-on bagggage, AND THE CHECK-IN STAFF ENFORCED IT!
Being cynical, I suspect some airlines see it as a source of extra income because flights are departing well under max weight limits coz no-one is taking checked-in luggage in an attempt to keep their costs down.
My spin on it, FWIW.
Le Vieux