Because that's how it works? They even document it themselves: https://help.duckduckgo.com/results/sources/?redir=1
Re:DuckDuckGo Search Improvements
by fredsanford on Tuesday October 15, 2019 @07:55PM
(#21265459)
Doesn't yahoo use bing for searches? I'd swear it did at one point.
duckduckgo-owned-server.yahoo.net ?
Same results and order as Yahoo on obscure keywords
Which keywords? I just searched (as posted above) for "extent space taco secure". It breaks bing. Yahoo returns results that are closer (including some shared oddities like storage units in Nashville), but they're still very distinctly unique.
You search for the thing and you find the thing. Why do you expect the results, especially the top results, to be different? Is there any other evidence that they are not doing searches themselves?