Maurice it seems that you are quite happy for our caravan to detached and cause injury or even death? Hopefully I have misinterpreted your post? Why should the two units separate and go on their separate ways? I have never heard of a caravan stopping almost immediately it detaches from the towing vehicle and it can run some distance before it comes to a halt as we all know that the brake cable is not very effective at stopping a caravan. Even on a car the handbrake is generally not that effective as both tend to use drum brakes instead of disc brakes. If the caravan with a chain does become detached and the driver is foolish enough to brake hard, the caravan can only run into the back of the car for the distance that the chains will allow which will only be inches rather than feet. The chain method is well and truly tested and proved to be effective. I am not familiar with electronic brakes so cannot really comment but suspect that the caravan will detach and try and find its own merry way which may not be merry for a third party. I think that the majority agree with you that something needs to be done to make the issue of a caravan detaching safer for all road suers and that should start with the driver of the towing vehicle!
If I remember correctly, the chain is welded onto the A frame and then looped over the towball so if the hitch became detached the caravan would remain attached to the towing vehicle as it would still be over the towball.
In SA if the caravan becomes unhitched, the chains stop the caravan from dropping onto the floor and the caravan stays behind the towing vehicle instead of the caravan running into oncoming traffic as the chain is looped over the towball on the car similar to how many brake cables are fitted onto the towing vehicle.