That's my main concern. Duckduckgo is used more than Bing in many countries and Microsoft might just cancel their access some day.
There is always Yandex I guess
There is always Yandex I guess
While I do believe Google has the superior search engine, there may also be an argument for denying them the "vertical integration of identity". That is, if you use Gmail and Google Search, Google can figure out more about you (in theory) than if you use just Gmail. Same reason I never -ever- use Facebook SSO for logging into non-Facebook sites.