Which has been almost abandoned since the developer left ReactOS contribution. There's no maintainer if one wants to contribute to Btrfs. IIRC, it was done to find a viable alternative for NTFS as it is almost as hard to develop ReactOS itself. Still, lack of an open source NTFS driver is the most important lack of ReactOS. Because many of the reliability issues are tied to filesystem reliability and FAT is not as reliable as NTFS. When you do a hard reset, registry might get corrupt because it could not flush to disk properly and without a Journaling file system, it's not easy to prevent, rollback, recover from this situation.