Two things become obvious at that point, and the main one is that other search engines don't just customize search results to individuals, they actually spend costly human resources currating and QA'ing results. DuckDuckGo's search results kind of suck, and the reason they're not as good is because the results are not groomed to the same degree, by as many eyes, nor to the same level of quality.
The other obvious thing quickly noticed is that DuckDuckGo's !bang operators are so, so, so much more handy than some of the other horrendously mangled, inscrutable query strings you wind up landing on, that would require 5 or 10 clicks, navigating the intended user interfaces of the parent sites that actually host the results.
Compare using !googleimages on DuckDuckGo, to what actually happens when you click and type for results at https://images.google.com?
It's kind of silly that you can't just pass a query string to Google, and that DuckDuckGo does their query strings better than Google does for it's own product.