Many people properly know much more then i Do. but a few point.
ZFS really is an FileSystem for Server Space. Since Apple is an Consumer company, how do their BEST selling products benefits from it, Macbook, and iPod / iPhone ?
ZFS - is not energy efficient. the amount of CPU cycles and memory required simply doesn't suit the current Consumer Mac.
ZFS is good, very good for servers, but how much revenue does apple earn from Servers?
TimeMachine and Snapshots, there are...