Compression is essential if you're uploading or downloading software, and it's very handy when you're trying to keep your disks from getting too cluttered. Compressing and decompressing files used to be simple, but things have changed.
Once upon a time, SEA (System Enhancements Associates) had the PC compression/decompression market all to itself with the original ARC. But competition soon surfaced in the form of PK Ware's PKARC, a program that was compatible with ARC but that also offered some unique features. SEA sued PKWare, saying that, among other things, it owned the ARC extension.
PKWare lost the court battle, but it may have won the war. As ordered by the court, Phil Katz, the force behind PKWare, abandoned PKARC