lots of info here mcboo: http://www.golefty.com/lefty.swf
Admittedly the site quite old, and some of the info doesn’t exactly hold true now but mainly why not? You may as well ask, why go mtb-ing?
Why single speed, why 6″ travel, why fat bike’s???… etc
There a bit different, a marmite fork even, but I wouldn’t suggest they’re perfect. Mine pretty damned light for a 140mm fork (1550g), extremely stiff, even though it’s pretty old (circa 2005 purchased by me in 2007[?]) but only been serviced twice – and not suffered for it (can many other forks say the same). I’ve not long spent a load of cash getting the damper upgraded – 2011 damper internal’s in a fork produced in 2005, as I do like mine.
I’ve always found it to be good fun (with some drawbacks) and best of all they annoy some people to the point of apoplexy.