Not the parent, but a stupid reason why I can't use DDG is that it doesn't support IPv6. It's extremely unhelpful when you're doing some IPv6-only testing and then can't search for answers.
As far as I can tell, 6 years ago the reason was that AWS didn't support IPv6[0]. It has for 2.5 years by now though.
[0] https://web.archive.org/web/20180909174057/https://duck.co/f...