IMVHO as SLF, part of this is down to the airlines themselves. Charging punters for checking bags encourages them to take as much in to the cabin as they can. It might be better to stop charging for checked bags, and impose a much tighter limit on materials permitted in the cabin (eg. a laptop bag, baby needs or medication bag), which could easily fit under a seat and not be a hold-up in an evacuation, even if grabbed. The overhead bins could then hold the IFE boxes.
Part of the checked bag issue, however, is the hassle factor in having to check bags at departure, and wait hopefully and patiently for them to emerge at the other end. Waiting 40 mins at EWR for a bag to come off an aircraft parked at the closest stand to the terminal building does not engender confidence in anything changing there, however.
Another motivation for the punters to carry on as much as possible is the tendency, to put it mildly, for items in checked luggage to go missing.
Now I am sure that everyone who handles the checked bag is of the utmost probity, but with the security services having free access to the bags...
I have not had anything lifted from checked bags, but I have spoken with many who have. Are all their claims accurate? Not sure but I see no reason not to believe them. Perhaps others could lend some insight into whether this is a real problem or not.