"I note that checked bags cannot block passengers from escaping an aircraft. Perhaps someone will someday quantify the additional risk airlines forced on passengers when they started charging for every bag."

I don't think this is as big a problem as one makes it out to be and here is why. There are certain things I need when I travel that I can't afford to go without in the case my checked bags don't make it to my destination at the same time as me. Things such as prescription medicine, contacts and my retainer (though not nearly as important as the previous two but still important none the less) are things I always carry on because they are things I can't easily replace if my bags are lost. Then I bring the entertainment, usually a laptop and/or a tablet and books/magazines. All of that stuff would need to be in at least one carry on.

Most, if not all, of the airlines I have flown have a limit to how many bags you can carry on. So it isn't like charging for check bags is going to have people start bringing 10 carry ons, it would have them bring the max if they wanted which as far as I know is 2 for most airlines.