"I am planning to build a tortured plywood or compound bend boat...The material I have read indicates that they are light, easy (tricky) to build, inexpensive with good stability. So, why don't more people build them? Any comment would be helpful."

You don't mention what "material" you have read but Chris's book the original "Kayak Shop" (one of my first boat building books) does contain a "tortured" boat called the "Yare". I had liked it for the reasons you mentioned and also considered building it. Mostly it was one of the first wood boats I had seen to build and it was so light. Apparently Chris has dropped (I have heard) this boat from his later book.I suspect the reasons for this method not being more popular (especially here in what is a forum for serious boat builders) is because of the following: It is very prone to ending up with a "twist" to the keel, perhaps this could be avoided but the method is not called "Tortured" for nothing. It is a rough and ready method for getting a little boat. Don't get me wrong every method and design has trade offs and win/lose choices (you take your pick). It is more a method a non boatbuilder may be attracted to for a not too complicated way to make an ok boat for a one time thing. It is less skill than just a matter of "torturing" the ply into something resembling a reasonable boat shape. All in all it is better than no boat and has other good things going for it such as, a non boatbuilder can use this method to get a boat that is light and good to play in (especially a person who doesn't really ever aspire to be a boatbuilder would be more attracted to this method because it gets you a boat, but the boat it gets you is not really a boat that a boatbuilder would want. Again this is especially true when there are so many better choices and methods out there for a boatbuilder to pick from). Since you say it is for kids this may even be another reason to build using this method, because they really just want to get on flat water and paddle, this boat is small and should be good for this purpose (by the way, check the beam width to make sure that this "Yare" or any other model you may build has enough intial stability for a child's use). I think this is a starting point that a person who was interesting in boatbuilding would perhaps start with, but learning would soon leave it behind to move on to better boatbuilding methods. Me for instance, like you I started out wanting to build the "Yare" but after learning and thinking what I wanted, I ended up building my first boat as a stripper. Good Luck!

Joe