In an effort to do some more research into this topic, I discovered a "guide to military costuming" in the world of the wheel. One thing I instantly noticed was that the most common standard-issue military apparel seems to be exactly this:

Helmet (sometimes with plumed)
Breastplate (sometimes embossed)
Coat
Breeches
Boots

Is this exclusive to light cavalry? Why is it that the only people I've ever seen fight in plate and mail are Borderlands, Whitecloaks, and people from Tar Valon and Andor? Is it because those nations are more rich and more capable of equipping their soldiers?

...I just didn't get it. Where's the variety? I mean, were there other pieces of the armor that were deliberately omitted (tassets, pauldrons, greaves, etc.) just because it wasn't pertinent to describe?