Well, now i gotta come here and told you why most of this shit is so.
Magical equipment, because of its magical nature, is pretty much indestructible by normal standards. This means a magical sword could slay a thousand mens without so much as lossing its sharpness. Of course most of stuff that is magical is not truly indestructible, just harder (the stronger the magic the more resistant the item) and can safely be used for its intented purpose indefinitely. Using a sword to hit stuff that is as hard as steel would be its intended purpose, using it as a lever to lift a fully loaded cart will more than likely break it, even with it enchanced durability and resistance.
Same principle applies to armor, unless you are facing a rust monster or some shit, your metal armor should be fine. This is the origin of it all, not sure how its treated in the world of the elder scrolls, because i really dont give a shit about its lore.
Of course, this asumes you are wearing magical equipment to start with. Differentiating one from the other (magical from non magical mechanic wise) in a game is a pain in the ass (im guessing). BG I sorta did this by making non magical weapons break because of the shit quality of the poisoned iron of the region, and that was cool. But there could be so much more, weapon maintenance up till you find your first magical item will make you cherish it all more.
Anyway, this steems from the fact that for gear management to be truly realistic detracts too much for the experience (minute, meaningless or uninteresting details should not be included, unless it is for flavour), so magic to the rescue being convenient and leaving all that behind. Magical armor adjusts to the wearers body as if it was custom made, it does not encumber the wearer (this is why in AD&D 2nd ed you could use your full dex modifier on a gothic plate), metal stuff should not rust, etc.