also some people use bangs [0] like !g !b !yt and other bang's to redirect search another website directly from ddg. (I use this when I do not like the responses and want to check another search engine)

sort of like google giving money to wikipedia, I suspect they do infact collect information on ddg searches and can aggregate it and make something useful from the information. in fact, they can probably infer that ddgs initial response was poor and determine their weaknesses etc

[0] https://duckduckgo.com/bang