[rando3826]

Because canonical wants to be the os of light weight vm images and docker images. You can't do that if the first step in distribution is always "boot into a separate filesystem, compile a kernel module, then reboot", and then if you want to distribute your image to anyone outside your organization, be sure to first remove that kernel module, and have them do the same process again.

[xenophonf]

The engineering problems are tractable even in those cases: Don't put the root file system on ZFS. Develop some kind of first-boot initrd that includes enough of a toolchain to build zfs.ko. I'm sure there are other, better ways to solve shipping ZFS in a virtual machine image, especially compared that to the legal and business risks of having a LTS release deemed a copyright infringement: Court costs, legal fees, fines, re-releasing Ubuntu, etc.

[rando3826]

I don't think they are tractable. They break the requirements.