Why should you care? Tech diversity is good, and people can try out different approaches. Aside from that, there’s not a reason. Systemd is a really good desktop init.
What is init freedom? It means the init system can be changed without other software breaking because there is a dependency on some functionality of the init. In this case, a dependency on systemd. Although it’s probably a dependency on a subproject under the systemd umbrella rather then systemd itself.
Why systemd? It’s tailored to weirdnesses in the Linux kernel. The Linux kernel isn’t perfect, and it’s user land isn’t tied to the kernel. Systemd is a shim which papers over the oddities. I don’t remember which oddities, but they’re there and people ignore them.
Were there dumb decisions made? Yes, especially for the server side. I should test out some other inits for servers, but it ultimately works fine.