It's because there are two ways to sync content across devices, paid sync through Obsidian vs. git. Given sync is a p0 feature, it seems logical that both get mentioned when the question arises.

Also, the app's really good, and I pay for Sync -- git works well, but it's a bit clumsier on iOS. Never posted a paid comment in my life.

It's the biggest & most popular app in the note-taking space. It's closed-source, which I don't love, and I've tried to look for alternatives, but there just isn't anything else that's as good as Obsidian. In a situation like that, you don't need to pay people to talk about your product. People will evangelize it on their own.