As humans, we like to believe a catastrophe like this will never happen to me - it can only affect other people
The first airline to impose a policy drastically limiting hand luggage for safety reasons (as opposed to 'not enough space in overhead lockers') will likely see a significant fall in sales revenue while competitors continuing to allow hand luggage unchanged will see a commercial gain.
If limiting hand luggage in a significant way is to happen, it has to either be via Govt passing law, or by airlines imposing a monetary charge for hand luggage (thus leading to many pax choosing to save money and cutting their hand luggage voluntarily). The events of 9/11 were a one-off and people accepted the hike in security screening temporarily because it was a one-off... persuading that 9/11 was the new normal was never going to work