As mentioned countless times already, it's all about aesthetics. Would you wear a poop if it had twenty more armour points than daedric? I doubt it, because it doesn't look awesome. And for most people it's all about looking as epic as humanly possible, so dragon smithing is far from useless.
Yes, actually I would. If Bethesda had rendered in a set of armor that was a skinned cat, sandals with socks, and a dunce hat. that had some absurd amount of armor. Yeah, I'd wear it.
People bring up, well lower level armor can reach the potential of higher level armor with enchants and blah. But what if I would rather use those perks or enchants towards other things. If my level 10 armor capped at and would have the same defense as my level 5 armor with 3 perks invested in it. But I like the level 5 armor better, I'm just [censored]. I'm taking the level10 armor and spending them 3 perks somewhere else. All people are saying is, well it's really a choice. If you invest heavily in perks, Iron armor can end up being just as good as dragon armor. Well what the [censored] is the point in there even being dragon armor for? If you're going to play this game based on everything logical about games. Better/higher level resources=higher level gear.
If people really wanted choices, they'd be talking about the lack of options in armor. Why does all Iron armor look the same, why does all steel armor look the same. Why can I not customize how my armor looks. Gear comes in progression, that's something every gamer knows and expects. If you thought otherwise, you're lying. It does not matter the reason, the top tier gear in this case regressed. And it's silly. Capped or not.