We all know that a level 35 character is not a fixed level of combat power. There is too much variation. Since I'm smithing and enchanting, the leveled items are all pretty much useless to me. They would be better if they leveled with you. Then someday, dragonbane might be useful.
Even if they leveled with you they would still be useless, since they can never match the damage or enchantments of self-made gear. Without crafting they're (significantly, in some cases) more useful, so having them not be leveled would make more sense, but they will eventually obsolesce no matter what.
The good part of having them being leveled is that a low-level character obtaining one cannot just stomp all over the opposition for an extended period, however that
does reduce the motivation to explore for some folks, since they cannot find that one 'special' item that makes dealing with a particularly nasty dungeon crawl worth the hassle. There is, unfortunately, no good solution to this, since making such items not available early means early exploration isn't very rewarding, but making them available early means there's no longer any challenge in obtaining more.
Sealing them behind powerful guardians doesn't work, because then you have the contradictory situation of either not needing them if you can actually obtain one of them, or being forever unable to get any of them because you need one of them to do so in the first place. Quest-gating works up to a point, however once a quest has been dissected on the forums and wiki then anyone can just waltz in and get the thing unless there's a level requirement, which in turn causes complaints about being artificially blocked from experiencing content at one's own pace. Essentially, we're asking for powerful items to be difficult to acquire yet potentially be obtained at an early level, which is a contradiction in terms and utterly impossible to design for.