A person would just about have to hit me to offend me. Once I ascertained why, there might be a throw-down....
I am well aware of "the flaw factor" as I have dealt with all types of antiques for the last 30 some years.
I see it mostly in Asian, Persian and Native American hand made items.
They are done intentionally.
I do it 'cause I like to ask people if they notice.....
You, my Friend, are very astute!
And I won't cloud your vision too much....
Just remember that in the "Land of the Blind,"
The one-eyed man is King!
Best Wishes Always,
Scott
Also, as it relates to psychology; Each person's creation, if flaws are intended, "personalize" their creation.
It's akin to Picasso signing his latest painting. In the medium of tapestries, rugs, beadwork, etc. there is really no other way for the creator of the piece to sign their work.
A few of the more prolific producers of pieces usually use very similar methods on each piece that they create.
I believe that other reasons may be in play, but upon this premise, I think culture plays a small role if any.