Most people definitely use whatever is preset in the browser, at least until someone shows them something better. But regarding the name, the situation is very similar to the one with Microsoft Word: if it isn't called that ("MS Word" ... or "Google"), it isn't "the real thing" and somewhat suspicious, people will refuse to use it on that grounds, no matter how many experts will tell them the other one is better, more secure etc.

Also, I'll mention it again: if you set ddg or anything else as selected search engine in FF Nightly, typing in the location bar will still search with Google. To change that, you need to mess with about:config. Justification? Money, I suppose...