For some reason fenders, tongues and lights take a real beating on trailers. People who barrow trailers don't own one and have very little knowledge on how to use one. Once it's hooked up they think it's going to go wherever they want it to so what's to worry about.
I've gotten to where I am very careful about who uses my stuff. If you think a trailer is bad what until you own a small excavator. Everybody and their mother thinks it would be fun to barrow one of those. Sure you can use my excavator but the operator comes with it. When they find out they can't operate it they are not nearly as interested.