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.
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.
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.