Why would someone do that? NTFS is stable, faster than btrfs and has all the same features.
Mind you, with openzfs (https://openzfsonwindows.org/) you get windows (flakey), freebsd, netbsd and linux but -as I said; I'm not sure zfs is super reliable on windows at this point.
Mind you, I just stick with ntfs -linux can see it, windows can see it and if there's extra features btrfs provides they're not ones I am missing.
There are millions of reasons to write software other than "faster" or "more features".
I can imagine this being convenient (albeit risky) when migrating Windows to Linux if you really can't afford a spare disk to backup all your data.
As the sibling comment mentioned, NTFS does have a case-sensitive mode, for instance for the POSIX subsystem (which no longer exists, but it existed back when NTFS was new); I think it's also used for WSL1. And NTFS does have per-file compression, I've used it myself back in the early 2000s (as it was a good way to free a bit of space on the small disks from back then); there was even a setting you could enable on Windows Explorer which made compressed files in its listing blue-colored.
NTFS had mediocre compression support from the very start that could be enabled on a volume or directory basis, but gained modern LZ-based compression (that could be extended to whatever algorithm you wanted) in Windows 10, but it’s unfortunately a per-file process that must be done post-write.