Just asked one of my kids;
"You're on a plane, it's on fire, you're been yelled at to evacuate, what's the most stupid thing you could possibly imagine doing next?"
He thought for quite a long time (several seconds) and said "fiddle around with the overhead locker getting my bag out?".
Obviously. But will your son actually act accordingly if he ever should find himself in a real emergency? You don't know - and neither does he.
When I trained to deploy one of our instructors had an anec***e. I don't know if it's real or just that, but: In some US city cops where training how to disarm an attacker with a gun. They'd train 1 on 1 with one acting as the attacker, the other as the cop. After the cop disarmed "the attacker" he'd hand back the pistol and they'd have another go. In other words: He was taught to hand back the gun to the attacker - which ended up getting him killed when handing a gun back to an actual attacker.
It's anec***al but not entirely unbelievable. When in an emergency, when stressed to the max, we tend to fall back on the procedures we know, lodged in our memory and our muscles, the acts our body remembers. And when we disembark a plane - we grab our carry-ons.
When I'm seated at an overwing exit I firmly believe that I'll act as I should, should an emergency occur. But can I say for sure that I won't be trying to push the door OUT and delay an evacuation, instead of pulling it towards myself, tilt it and throw it out of the plane as I should? No. We probably all imagine ourselves as the one who's cool, calm and collected and saves the day - but until we've been there we don't know how we'll react. And to rely on the threat of prosecution to get PAX to leave their carry-ons behind is missing the point of human nature entirely.
Just saying.