“If you already know the village or district where your ancestors lived, do you learn anything useful from getting this DNA information?”
Maybe which conquering army marched through back in the day.
The wonderful thing about these DNA studies, when offered by Surname Associations (groups of genealogists with the same surname in their tree, and often the same descent) is that, what shows up in the paper trail, turns out to have been concealing various promiscuities, undocumented adoptions, backdoor men, Neandertals-in-the-woodpile, and that kind of thing. IOW, what’s written ain’t necessary so. :’)