Lets face it, there is a fundamental problem of perception with the "zero up front, pick-your-pocket" LCC model
I don't think the extra cost is the issue in most cases (no pun intended).
I think most passengers now carry oversized bags into the cabin simply because they can't be bothered spending the extra time waiting for their luggage at the destination airport carousel.
The number of times I've seen passengers trying to stuff obviously oversized wheeled suitcases into the overhead lockers is mind boggling, resulting in the flight attendants then having to take the suitcase "somewhere down the back".
I am amazed that the airlines and/or CASA don't enforce the cabin luggage requirement as they are scanning the boarding passes (have you seen anyone use those "acceptable luggage racks" that are stationed at every airport departure lounge?) as some of these bags would represent a serious safety hazard in the event of a crash landing and the overhead lockers sprung open disgorging suitcases everywhere.
Can anyone give a reason why the airlines don't enforce the cabin baggage requirement more stringently? Is it because they are scared they will lose customers if they are too diligent?