Comments like yours come up whenever anyone dares discuss ZFS or FreeBSD. Sure, you can use Btrfs, xfs, ext4 or whatever the hell you want on Linux if you want. Nobody is trying to take away your toys. But Linux is already dominant -- you don't need to convince people to use Linux. FreeBSD, however, doesn't get attention it deserves. Hence why threads like these occasionally pop up.

And for what it's worth, ZFS development pre-dates Btrfs. You can make all the arguments for Btrfs that you want but ZFS is still the vastly more mature filesystem out of the two. Hence why the few examples people can come up with regards to Btrfs usage are companies with the resources of Facebook (as opposed to ZFS which is used by companies large and small).