Shorten
Shorten is one of the oldest Lossless audio formats. It was creader by Tony Robinson in the mid-nineties.
It lacks several features like seekability (although there is a "hack" that adds seek support), streamability, support for Multichannel and high sampling rates, tagging...
The reason why it became very popular is that it was the first open source lossless compressor. It gained huge momentum years ago because of it, and to this day it's the most popular format for lossless audio encoding, being used mostly at live recordings (bootlegs) trading communities.