XFS really shines when you're dealing with large volumes, especially with RAID. There are certain features, like striped allocation, that mean you end up getting faster performance, because the filesystem has a better idea of how blocks are laid out on the disks.
I personally still consider XFS a very mature and reliable filesystem. Both in terms of utility programs and kernel implementation. If I remember correctly, it was ported to linux from SGI/Irix where it was used for decades. It also was the default fs for RedHat/centos for a long time, so it might still have stuck at many shops.
Heres my anecdotal datapoint on which I base my personal believe:
From about 10-6 years ago, when I was doing sysadmin-work at university building storage-systems from commodity parts for experimental bulk data, we first had a load of not-reliably working early raid/sata(?) adapters, and those made ext3 and reiserfs (I think...) oops the kernel when the on-disk structure went bad. Whereas XFS just put a "XFS: remounted FS readonly due to errors" in the kernel logfile. That experience made XFS my default filesystem up to recently when I started to switch to btrfs. (of course, we fixed the hardware-errors, too... :-) )
Also, from that time, I got to use xfsdump/xfsrestore for backups and storage of fs-images which not even once failed on me.
As a blithe, new-Linux user (3.5 years), I was bumfuzzled when I saw RHEL/CentOS 7 switched from ext4 to XFS, figuring it to be some young upstart stealing the crown from the king. Then I did some Googling and figured out that XFS is as old as ext2! I'm looking forward to discovering how tools like xfs* can make my life easier.
ext2/3/4 have terrible large-directory performance. If you create 100,000 files in a directory in an ext2/3/4 filesystem, enumerating said files (ls, readdir, etc.) becomes unbearably slow -- and the slowness persists even after you delete all but one of the files in the directory.
The lure of "ohhh shiny!" is prevalent in tech. I love to use bleeding edge stuff, play with new toys etc, but that is purely for home and personal stuff. Never for work.
I want my work life to be utterly boring. Nothing breaking. Everything behaving exactly as expected.
I will happily trade a bit of performance and a lack of some shiny features for a system or component that works reliably. The less time I have to spend fighting stuff the more time I can spend tuning, automating or improving what I do have to look after.
XFS performs well. It's reliable, reasonably fast (they trade some speed for durability/reliability), and just works
Why?