[jandrewrogers]

If I had to guess, it is because ZFS likes to insert itself into things beyond just being a filesystem. It is one of the reasons ZFS notoriously works poorly with database engines, which have a tendency to bypass or ignore the filesystem (for good reason). It is a design choice on the part of ZFS.

[panick21_]

Oracle specifically came back to Sun because they had ZFS based servers. So that seems a bit strange to me.