Because the world-building demands it, that's why the humans use standards stuff, because humans are standard.

I've always seen Human stuff as "standard." It's easy to mass produce, reliable, and in the end, durable. Human stonework is easy to construct, and lasts for a good long time, and though their weapons may not be super fancy, as the ancient nord weapons show, they can still hold a decent edge though sands of years later. Although the Elven races make priceless weapons, in the end, humans make more stuff, faster.

You see those warriors from Hammerfell? They've got curved swords! Curved. Swords.

Well humans don't live as long either. They don't need their stuff to last as long.

Humans are good armourers. Nordic plate is barely weaker than Orcish. Nordic Scalemail is better than Elven. And all those Dragonbone stuff, they could've only been made by humans, and they're better than Ebony.

Some of those Barrows are pretty damn impressive. When I first saw Solitude my jaw dropped. Labyrinthian is pretty impressive, and Shalidor's maze.

An example of amazing human architecture would be Frostcrag Spire. Of course, the original designer may not be human. He is a distant relative of the PC.

The Dawnguard castle. Beat that.

Barrows
Imperial outposts, forts, and towns
Nordic arms and armor
College of Winterhold
Windhelm
Anvil
Ebonheart
Redguard ships

Well ancient things are almost always better made because they had to be at the time. Compare the pyramids to the average skyscraqer made today, which one is likely to last the longest? Obviously not the skyscraqer without proper maintenance. I wouldn't say the humans devolved they just outgrew the need to make things that last.

Not just Dragonbone armor. Dragonscale armor as well. In TES IIIit was an Imperial armor. In Skyrim if it's not an Imperial design, it's Nordic.

As for steel, in addition to the Steel Plate in TES V, in TES IV, Blackwood Company armor, which I presume to be of Imperial make, was superior to Dwemer armor. And I suspect most Ebony gear outside of Morrowind is made by non-Dunmer. The Ebony gear in TES IV was certainly not of Dunmer design.

Dragonscale is an Akaviri design, actually.

But, still mannish.

Quantity versus quality. Dumner make glass armour and live in giant insects; they also make netch leather armour and live in shacks. Most Orsimer in Skyrim don't wear Orcish armour. We've never been to Alinor, so we really don't know what common Altmer material culture is like.

Also, good luck hiring a Telvanni to grow you a tower, or goading a gaint crab to die just where you need it. Responsible Architecture doesn't seem like something that could be easily transplanted.

Bolded the important bit. When I explain how Romans beat the barbarians to people despite the barbarians even today having a reputation as fearsome warriors, it's because they were fearsome individually, but that wasn't enough against the mass of cold, hard Roman discipline.

Move that to tamriel. Imperials have a reputation as great persuaders and unifiers. In Morrowind, other soldiers won't even speak to an out-of-uniform legionnaire. Cold, hard discipline trumped the superior equipment of the various individuals they fought. Where it didn't, they hit you with a robot.

In the case of the Redoran, there's also the numbers issue. Both the Redoran and the Legion seem like disciplined, tightly organized armies, but the Legion has the advantage of more "modern" tactics unimpeded by that overwhelming sense of tradition and fair-play that the Redoran are bound to. They're just smarter tacticians. They also have numbers on the Redoran, who've been constantly shrinking due to the predations of the Nords, Dagoth Ur, and House Hlaalu.

Didn't the Imperials have a moon colony? And we had several pretty skilled Breton in Morrowind (Remember Louis Beauchamp, who built an airship?_
Frankly all the races have some redeemable stuff-makings.

They did if I remember correctly. Imperials had airships in the Second Era too (hell, they probably had spaceships by the Second Era). Altmer had/have Sunbirds, but those are actual birds. Khajiit get high can use moon sugar to walk to the moon too...once again, if I remember correctly.

Another strange construct is that the Argonians have bubbles/amoebas/bugs that they use as a train system through the Hist's roots (even if they aren't men, but at least they aren't elves).

Rome only beat the Gauls through persistence. The Gauls beat them back plenty of times. It took several hundred years before they were finally conquered by Julius Caesar.

Yep, they http://www.gamesas.com/topic/1327177-tatterdemalion-the-lunar-province-of-secunda/ http://www.gamesas.com/topic/1336585-tiber-septim%E2%80%99s-sword-meeting-with-cyrus-the-restless/. Or rather, voidships.