Weaker... According to whom? I particularly use DDG on my personal devices and only occasionally go to Google. Whenever I'm using a machine that use Google as the default, I often go back to DDG to get results unspoiled by the bias pushed by Google's agenda, SEO and paid ads.

But answering your question, it could let the user choose their search engine as part of the onboarding experience while providing a random preselected default.