This is a classic tragedy-of-the-commons problem. From one individual's perspective, you think to yourself that grabbing your bag only takes 1 additional second, and it's pretty unlikely that you'll get hurt just because of that additional second. Compared to the upside of not losing your precious belongings, that seems like an understandable cost-benefit analysis.

The problem is, you aren't just delaying yourself by 1 second, you're also delaying the other 100 people behind you by 1 second. And if you multiply the risks involved by 100, the outcome of the cost-benefit analysis changes dramatically.

We could yell at people for being too dumb to do the "right thing", but let's be honest, this isn't the kind of issue that will filter down to everyone in society. Unless it makes the front page of NYTimes or CNN, the vast majority of people will never get to hear your moral lectures and explanations. And airlines don't want to unduly alarm their passengers on the vast majority of flights which won't have problems, so they aren't going to spend too much effort on this either. The best solution here is some simple technology. Equip all the overhead bins with central locks, so that once a switch is flipped, it's impossible for a passenger to get them open. This way, people won't even have the chance to grab their luggage, and we wouldn't have to sit here having this discussion.