well, cars and trucks usually don't have a hanger for the leaf spring and that is usually what wears the most on a trailer. and the hanger is pretty thin material.
The thick hanger that comes with wet bolts solves the problem.
Next, they use a very thin plastic sleave over a steel bolt in the eylets. doesn't take long for the plastic sleave to wear through, then you get lots of clearance and slop.
and when turning a trailer has much much higher side loads pn the axles and springs than a car/truck since the trailer pivots on the dual axles.