In my case, because it's what Ubuntu "supports" for bootable root crypto ZFS, and I wanted to try it.
I've run ZFS on top of LUKS for my backup storage servers for probably over a decade now, and it works fine. But it wasn't really an option for my workstation.
That said, I'm not really sure what benefit I'm gaining from ZFS on my desktop. I've got that snapshots which are definitely nice. I've used it a couple times to go back in time. In theory I can go back if I wedge the system through package installs or an OS upgrade, but I've not done that (yet). It does slow down package installs because of taking snapshots, but that's ok generally.
And in my experience LUKS works great.
It's a very cleanly layered system, it just doesn't bother end user with details (as implementor, you can play with them, thus LustreZFS): there's separate SPA (block), DMU (OSD) and ZPL (FS) & ZVOL (emulated block device) layers.
Compression and encryption are integrated at DMU level because that's a logical place for them.
NFS actually calls OS nfs server.
Interesting; it'd been claimed to me before that ZFS had its own NFS server (or I guess the OpenSolaris NFS server) included but that nobody used it because it was old/buggy. A quick glance at https://github.com/openzfs/openzfs/ (the old archived version based on illumos, if I read correctly) implies that this might have been true at one point, but indeed https://github.com/openzfs/zfs doesn't seem to do its own NFS so it's not true now if it ever was. Thanks for correcting my understanding.
I believe that the modularity will only proof itself when external (as in, from unrelated people) projects becomes established and we see how well the original project maintains compatibility.
(I must say I wonder how big the intersection of people-who-like-ZFS and people-who-like-systemd is; they seemed to originate from very different cliques but there's no reason people who like one would dislike the other…)
