The quality of clothing issued during the Civil War and Indian Wars was indeed shoddy - and that's where we got that term, so look it up.
Contracts were let with no sizes specified, so the manufacturers would measure to get the largest number of garments from each bolt of cloth - resulting in the survival of so many of those small shell jackets one used to see that were in such good condition.
They were in that condition simply because no one could wear them, so they stayed baled up.
Additionally, manufacturers didn't pre-shrink any of their fabrics, so the shrinkage happened after the delivery of goods and initial issue - meaning that the poorly-paid soldier footed the bill.
The hats were laughable - often collapsing during the first rain - never to return to their original shape.
Vermin was always a problem on Campaign - men often cut their hair close in order to better find body lice, and used lye-based or pine tar soaps in the effort to keep clean, but back then, they weren't as germophobic as those of today, and they lived through the experience.
As to ridding clothing of vermin - anthills were quite often the solution, as was the 'chasing' of lice with candles by running the flame along the seams, or by the use of a red-hot wire - and in answer to the next observation - yes, it often burned holes in the clothing.
Campaigning was tough - tough on men - tough on horses - tough on equipment.
Everyone and everything took a beating, and often returned to Post in tatters - their clothing barely covering them, and their boots worn out.
It's why the actual campaign clothing used by the Indian Wars soldiers and troopers is so difficult to find - most of it ended up on the burn piles as too worn to even use to patch other things, and that says something more about uniform quality when one realizes that they never wasted anything if they could possibly help it, because they were never sure when (or if) they'd be resupplied, so they 'made do'.
Scouts Out!