This is because Google also tries to build a profile for you and serves different results based on that, while DDG will return the same thing for the same keywords to different people.

For searches in specific domains it is better to use bangs. For example prefixing with !py shows results from python manual.

Here's more about it: https://duckduckgo.com/bang

I've found this to be true for Bing too. For general search, it matches Google in accuracy. But in the case when I want to find a specific compilation error, only Google gives me useful results. But I still use Bing, and switch to Google only for such stuff.