GDPR is what changed this. Before that, registrars had little incentive to hide it for free when they could instead charge you for the service. It was not trivial that Google Domains (rip) came with free privacy proxy right from the beginning.
One can see this in practice in that company registration information is usually still available (through often behind a captcha), while personal information of private registrations require additional steps to demonstrate a legitimate interest. All this is also generally occurring at the registry level, rather than at the registrar.
It should be mentioned that privacy proxy is very similar to a straw man registration. If the registered owner is the proxy, then you are trusting that the proxy will honor the contract that is linking you with the property.
And yet all German sites must have such thing: https://0pointer.net/imprint
Mastodon _instances_ have Impressumspflicht, sure. But normal users don‘t and I have never seen anything contrary about private accounts.
Edit: unless the Account is for/by a business of course.
https://allaboutberlin.com/guides/website-compliance-germany...
If I were some kind of crazy maniac, I could pay him a visit and shut down systemd for good. You see why having this information out there is dangerous?