I call BS. There are many times when I catch a flight with a connector, and my luggage goes nonstop, or vice versa. What you speak of was the "old" method where we thought that muzzies would not blow themselves up. Bags are now screened in a different fashion, because the old method jammed up flight schedules. Suffice that if you are going somewhere for more than a day or two domestic or international, UPS, Airborne, and FedEX are GREAT ways to send your stuff in advance. Some of us do this every week. Guess what? A freight tracking number works much better than dealing with the gorilla in baggage claim. And you get out of the airport an hour earlier. It is not a crime to fly without luggage. Yet.
Just 3 weeks ago, I tried to check my luggage 6 hours before my flight and was told I could not.
I have also been on a plane when a passenger deplaned and our plane was delayed while that passenger's luggage was removed.
Of course luggage doesn't always accompany a passenger --- several times my luggage comes in on the next flight --- but when a passenger deplanes, you watch and see what happens.