Some of the items you mention are aftermarket parts. It is rare that any aftermarket parts will ever survive any significant exposure (one or two seasons at most, especially in the rust belt). The fact is that most aftermarket companies never test their products to the extent of the OEMs, nor do they have access to proper testing facilities. Even if they did, most aftermarket companies take the cheapest route to production and in the rare occurrence when they design a part that matches (or exceeds) OEM design specifications it's usually by luck alone. Many companies that over design their parts do so because of ignorance regarding engineering requirements i.e. make it stronger by making it thicker as opposed to improvement in part geometry or analysis of situational stress. The reason parts seem to rust too soon is because usually they aren't thoroughly designed to begin with. There are occasions where OEM parts fail prematurely due to failures in design or poor manufacturing but these are more rare than you think. Also, don't forget that surface corrosion, while unattractive, most often does not represent a mechanical failure in the part and poses no danger to the effectiveness in performance of the part. We're all in the same proverbial boat so I'm sympathetic to your concerns and your disappointment, but your expectations may be a bit too high i.e. rock rails actually doing their job will be damaged as they are designed to do (sacrificed for the protection of your vehicle) and as a result will rust. If they are rusting without being touched by anything other than the elements they do so because they are poorly designed.
