Comment by 8fingerlouie

What would Apple's incentive be to support Btrfs, Ext4, XFS or ZFS ?

Btrfs, Ext4 and XFS are all under GPLv3, which may or may not be a problem for Apple, but "just in case".

They tried with ZFS, but couldn't strike a deal with Sun/Oracle, so instead invented APFS.

Apple already delivers a stable filesystem. It may not be "best of breed", but it works, as billions of devices runs on it every day with zero problems.