It's plainly obvious why they don't. Oracle still sells *their* fork of ZFS.
Back in the pre-oracle days Sun's fishworks division sold ZFS-based storage appliances. Oracle still sells those, and thanks to ZFS' reputation they're still profitable. Oracle simply took that much older fork of ZFS (with no OpenZFS code in it) and made it closed-source.
Before anyone asks, no, that fork is too old and too diverged to be compatible with OpenZFS.
All the more reason for Oracle to someday do something to put all those Linux ZFS servers into a questionable legal status. They could then stand with a carrot in their other hand, waving their own unquestionably legal version of “ZFS”.
I don't think you understand how this works. Sun already gave all their power away via the CDDL.
We're currently in a legally-stable state, and have been for over a decade now (nearly two). If they could have done something, they would have.
The fact is that so long as nobody tries to merge ZFS code into the mainline kernel, there's nothing they can do. Everybody knows this, everybody agrees that would be a dumb idea, and everybody has agreed not to do it.
Back in the pre-oracle days Sun's fishworks division sold ZFS-based storage appliances. Oracle still sells those, and thanks to ZFS' reputation they're still profitable. Oracle simply took that much older fork of ZFS (with no OpenZFS code in it) and made it closed-source.
Before anyone asks, no, that fork is too old and too diverged to be compatible with OpenZFS.