Because the privacy concerning aspects are literally irrelevant.

These are set for testing/development purposes. For which the priorities are availability/reliability/speed. For those criteria, Google/Cloudflare are empirically the best worldwide.

This literally is used for test-resolving that at best probably would identify a systemd-dev. Everyone else shouldn't care because it's overwritten by distro maintainers.

Could you give more details about these tests and why the tests can't be modified to set DNS/NTP?

Likely unit tests... https://github.com/systemd/systemd/tree/master/test/test-res...

I assume some of these use it.

>why the tests can't be modified to set DNS/NTP?

I am not a systemd maintainer, they probably could be adjusted, but frankly I don't imagine they or I care enough to do so.

Like I said, this change only affects the devs, so why should it matter to anyone else.

Google offers better documentation than most, and the privacy aspects are good. [1] Of course you have to trust them but that would be true for any company. Given that the natural default would be even less trustworthy ISP, is not that bad.

https://developers.google.com/speed/public-dns/faq

i set up a bind nameserver for my internal network, and mistakenly i did not set upstream resolvers.

It's working anyway, i think it's resolving off the root nameservers...

I guess... You couldn't go more private than that.