What’s so bad about being based in the US?
This is all speculation (though informed by the Snowden revelations), but if the NSA asks DDG for data for some legitimate reason, it is likely that the NSA would just demand "all" the data, and not a scoped version of it. Meaning your information could get caught up in it.
I agree that for most people this may not be a concern, but if you would like to learn more, privacytools.io has some more information about the "14 Eyes" and other nation state information gathering efforts.
Edit: Okay, you can't really have evidence of absence, but good reasons to believe they don't log?
Though I have no way of verifying they don't keep logs, if I discover they do: at least I can sue them for it.