MilesAhead, I've wondered about this, too. I already have DDG set as the engine in the Firefox search box, and I just found that if I highlight a word or words and right-click, one of the options is "Search DuckDuckGo for [search term]". So what more could an add-on provide? (Indeed, I even checked my add-on list to be sure that the DDG Add-on wasn't already there.)