Does any not pull their emergency trailer brake cable?

Normally when a trailer comes loose the chains will keep it behind the tow truck , all mine did . I have had no damage by coasting to a stop . Mostly what causes a trailer to come loose is the transition from a driveway or a large bump of some kind , the trailer lifts off and drops onto the chains . All trailer hook ups are different , length of chains is important , they should catch the trailer before it touches the ground , if chains are too long at hook up you can twist them round and round and shorten them .
In the movies and on these forums the trailer always comes completely off and strikes a school bus full of kids and then careens into a fuel supply dump ! Some times we go weeks without that happening . Make sure your breakaway works , make sure your chains are right and watch out for school buses!