Wood is amazing stuff.
Teak and Locust are famously water- and rot- resistant. Ipe and most hardwoods are famously strong. Balsa and many softwoods are famously light. Most species are naturally buoyant. All are compatible with any number of treatments - coatings, preservatives, etc.
It's almost always cheaper to obtain and easier to work (without specialized tooling, welding equipment, etc.) than would be ANY comparable metal.
It's a traditional material for boats, fences, siding, railroad ties, telephone poles, (weather resistance); house framing, furniture, wagons, wheels, (strength); crude machines, bridges, even airplanes (flexibility). I'd love to have a retro-tech 1850's TC!
2013 Travel Lite 960RX
2001 Ford F350 Diesel Super Cab Long Bed