IIRC, the carry-on limitation was more of an operational concern rather than one of security. The TSA or DOT was focused on the promise of getting everyone through security in 10-15 minutes. They felt that would be much more difficult if they didn't impose limitations on the # of items each pax could bring airside. So that I believe was the prime motivator for restricting the carry-on policy.

As for why I will always carry-on my bags when I'm able...last night I spent waiting 30 minutes at DFW C25 baggage claim for the bags from the PHX flight to start coming out of the carousel. Then it took about another 20 minutes for all of the bags to finish coming through and for me to realize mine was not among them.

So I stood in line for 10 minutes for an agent to tell me much what she told HKG_Flyer1. Add 10 minutes to travel to A27 where the next PHX flight came in, plus another 5 minutes waiting to let a baggage services person know that my bag made it on the later flight, we're already at 75 minutes since exiting the plane. If I carry on, I'm in my car and on the way home 15-20 minutes after I exit the jetway.

When both operational performance as well as the security of checked baggage increases, then I will consider checking bags again. But the delay in baggage retrieval, combined with the absolute fear and worry I went through last night about my personal belongings which would cost far more than AA's liability limitation to replace, I will continue to carry on my roller bag and laptop case.