It’s advertising. Plain and simple.

• The ethnicity estimates are a way for AncestryDNA to market their tests.  It’s marketing. It’s also how shoes and beer are sold. If you think it is a stretch to make beer “sexy,” try doing that for ethnicity results.
• The ethnicity estimates are not for your “immediate” ancestors, but for dozens of generations (at the very least) before the present day. They don’t tell you where great-grandpa emigrated from no matter what the advertising says. Those shoes don’t really make you sexy either.
• You may locate new first cousins, half-siblings, or uncles/aunts that were the result of a “short-term” relationship.  So maybe that marketing for the beer and shoes did actually work at some point in time.

Don’t get me wrong. Sometimes the ethnicity estimates are accurate (they do have some limited uses) and sometimes “new” relatives are welcomed with open arms. But sometimes they are not.

Remember that all the “DNA ads” are to get people to make a purchase–just like ads for anything else.

The upside of the ads is that more people test–and that may help you solve genealogical problems even if those testers don’t have trees and don’t respond to your inquiries. Non-responsive test takers with no trees frustrate me as well, but at least they are another test to sort through.