Firstly because there are many more salvage programs out there supporting FFS and secondly because FFS stores data in such a redundant manner that it's easy to recover files from a damaged partition.
For all it's drawbacks, I can say that in 22 continuous years of using FFS, I have never lost even a single file, except due to hard disk physical failure (not the fault of FFS). Of course, I have resorted to DiskSalv many times - thank you Dave Haynie.
