Ah, didn't know that. Then the main reason to use DDG would be if their "we don't track your searches" claim is honest. (Which I think it probably is; certainly I've seen no evidence that DDG is lying about not tracking your searches).

Even if they're only a layer around Bing, having your Bing searches coming from DDG's IP addresses rather than from your own IP address almost certainly makes it harder for Bing to track you, since your searches are being pooled with everyone else who uses DDG. Naturally, Google will track you, your computer, your phone, and would even track your dog and your Roomba if they could figure out how.