The real power is in the "bangs", though; you can use the `!` to immediately jump to the first search result without seeing a search page, or use `!g` to switch to Google for this particular query, among others. It enables a sort of power-user usage that one wouldn't get with Google.
I understand that for some people that's not enough of a time savings to make a difference, but I know DDG well enough to be able to `!` things and almost always immediately get to a successful result. I treat it as an extension of my brain at this point.
I used to configure those as search keywords in Firefox (and before, Opera), which do roughly the same without the exclamation point. But on a new browser, even just configuring your favourite top 5 searches is a lot of hassle compared to just setting DDG as the default search and using their bangs.
If I'm working on python and numpy and I want to look up `argsort`, I know I want to search the numpy page, so !numpy argsort takes me right there.
Any kind of web dev is !mdn whatever and I don't have to scroll through a dozen BS tutorials, I just get the specs.