I do find damaged clothing on the floor at Value Village, St Vincent de Paul, and Goodwill occasionally, but when I hand such items to an employee, they whisk them away. In my area, there are very few small church- or hospital-/charity-run thrifts. Their prices tend to run high, which is why I don't go out of my way to shop them, but I've rarely found badly damaged items in them.
The Pacific Northwest doesn't have a big moth* problem, so I find very little moth damage. When I do, I tend to assume it came in when somebody moved.
* Or ticks, chiggers, mosquitoes, fire ants, poisonous spiders, or scorpions, Fruit flies and meal moths, we got.
** Or poison oak/ivy/sumac, tornadoes, hurricanes, major droughts, etc. We do get earthquakes. Oh yeah. And rain.