"Also it would be dangerous to turn because who would turn such wood in their shop"
Actually, I've turned PT wood in my shop. I understood the danger, but because I need to make something from treated lumber, I took appropriate precautions. I've also turned Trex (an artificial timber made from sawdust and recycled milk cartons) and quite a few varieties of both ordinary and exotic woods.
Many people have allergies to wood. Capt Eddie frequently talks about his padauk allergy, and I have a woodturner friend who is allergic to lacewood. If you understand the issue and take the necessary precautions, you can work with just about any material you choose.
At a more fundamental level - woodturning involves a degree of danger regardless of the material being used. A block of dense wood spinning at high speed that has the potential of flying off and hitting the turner in the face. "Scary sharp' tools. Catches that can shatter steel tools. And all kinds of fine dust that can get into the lungs to cause permanent damage. But those of us who are involved in turning understand the risks, take precautions, and (usually) manage to avoid most of the harm.
While it has no meaning to me, there are those who have an emotional attachment to the Atlantic City Boardwalk and who would appreciate having something made from the wood. And there are woodturners who will respond to that 'market demand' by offering products. That's the way free enterprise works.
