They have....I tried one once when fishing on the Shenandoah. I prefer a standard kayak.
You're thinking of whitewater style kayaks. This type of kayak is very hard, near impossible to flip. I can stand up on mind and it won't flip.But still, you need to have a paddle with you no matter what.
Yes, you're right. They're not new though the newer ones do work better they used to.
Stability comes from the width of the kayak (hull shape plays a part as well). Most of the twin hull styles aren't actually wider than other styles and they don't really offer any real advantages. That's one reason they aren't real popular, they're also heavier and a little harder to control as well. The vast majority of kayak accidents are caused by plain old stupidity, like kayaking in flooded streams/rivers. Some of the cheaper sit in kayaks can tip if you're not careful, but the better designed ones and the SOP kayaks are near impossible to flip.I think 7 people in Wisconsin have drown so far this year in kayaking incidents. Fire departments are kept busy rescuing kayakers. Outriggers on kayaks is a good idea. I don't know how people would use those kayaks with things sticking out of the bottom like those shown. Kayaks, like canoes are often used because they can go through shallow water and narrow places. One kayak manufacturer has said that many of their cheaper products were designed for shallow water. I've seen kayaks with pedals and a propeller many years ago before kayaks got so popular.
There are twin hull models that are more stable.
I could be wrong and this might be seen not long from now as a useful innovation that becomes preferred.
