I think it is about how well people take care of their trailers. Says more about being a throw away society than it does the trailers being throw away. If people did the maintenance on their trailers like they are supposed to, I think most trailers would last 20 years or more. Most people I talk to at best check their roofs yearly, wash and wax their trailer once a year maybe, fix it when it's broken but really don't give it a thorough inspection on all parts and appliances.
I walk the roof every spring, every fall, seal or fix anything that looks like it might begin to be a problem. Wash the trailer after every trip, wax it twice a year (spring and fall), spray the stab jacks every other trip or so with silicone lub, check the water heater, furnace, frig vents a couple times a year and a general walk around inspection checking lights,windows, trim and the sealant around them. I'm hoping to get 15-20 years out of mine or at a minimum, get top dollar for it when I trade up once I retire.