As for rsync, sftp, scp those are heavily tied to ssh, rsync to the point that you actually ssh to host and call rsync command. rsync has a server mode as well, but almost no one uses it.

That aside, you can use FTP for auth and ACL in of which HTTP and rsync just aren't capable. I'm not sure this is a flaw in the core protocol so much as the tooling, but there you have it. FTP config syntax may often be byzantine. But it's widely supported (especially on old, low-spec, or embedded devices). For newer stuff, yeah sftp is probably better. But it's still got its uses.