Why does Dodge go cheap with their steel?

This is an issue pretty specific to Ram trucks apparently. After a quick google search it looks like Dodge never has done a great job of sealing the wheel well and salt is getting in behind the fender. It's a shame because I really like the looks of the Rams but that rust is a deal breaker. Ford and Chevy does rust in the same spot but not as quick or as bad as rams do.
I'm in Central New York and we wicked rust issues similar to what you have. We have a body shop here that offers Rust Check. I think it essentially is Fluid Film( Think a heavy Wd40 that never dries and dirt doesn't cling to it) that they spray in a similar manner to undercoating. It's $175 once a year. Easily a worthy investment if you keep your vehicle for many years.