I don't think this is an issue with DuckDuckGo...
Myself checked with the DDG and I found relevant information associated with bitcoin. Maybe there is something wrong with your browser.
Use DDG and try to search for "bitcoin wallet", let me know what the first result is..
Btw Qwant gives the same result.
Poeple don't search for "bitcoin" and simply that they use more search terms, so some test, if you use DGG and search for things like bitcoin miners 4 out of the first ten results are could mining scams.