I'm thinking durability (tabs popping in extreme use) and porosity (over time with exposure to sun / cold, etc.) may be a reason. if someone did
release a SUL sail (say FS) you can bet they would charge an arm and a leg (ref: Speed, Ozone Chrono, etc.). That's just my $0.02 (and I got into the
kiting world back in 1993 with SULs and dual line flying)
Depower Quiver: 14m Gin Eskimo, 10m Gin Eskimo III, 6m Gin Yeti, 4.5m Gin Yeti (custom bridle and mixer)
Fixed Bridle Quiver: MAC Bego 400, JOJO ET Instinct 2.5 & 5.5, Lil Devil 1.5, Sting 1.2
Rides: Ground Industries