I think this all comes down to static load vs. dynamic load. The trailer must be able to support the gross weight stated while going down the road, bouncing over bumps. Just think how much real load is on the suspension and frame as the trailer lands on the wheels after a bump, many times the actual weight of the trailer. In a static condition while camping, the frame and suspension can handle that same load. That is a number nobody really knows, but should far exceed the amount of people and gear that can fit in anyone's trailer.
So here is a good question: If I have a trailer that weights 5000 lbs, what is the actual load on the frame, suspension, wheels and tires as it lands after going over a good sized bump?
2015 Starcraft Travel Star 299BHU Black Pearl Edition
2011 Jayco X23J (traded in)
2009 Ford F150 FX4 SuperCrew