SUSE reaffirms support for Btrfs

At the end of the day, at any given moment, there's a "largest size available". Simply buying a bigger disk isn't possible, and RAID-10 uses space very inefficiently.

Not all applications are terribly sensitive to performance. A lot of the classical file servers have files that are effectively static - with occasional updates.

A home media server is another example: you can record multiple channels of 1080 video (Using ATSC / MPEG-2), and playback multiple recordings simultaneously, without skipping. Why target performance (which you don't need), and sacrifice storage space (which you do need).

Ther is simply no one size fits all solution; it's all a compromise. I personally use RAID6 when performance isn't a problem.