Fiberglass is really fast and cheap, and you can throw together a simple mold with wood. Hard to see 3d printing competing in the space of just making useful boats.
Fiberglass is incredibly useful for prototyping and repairs. I watched a shipwright rebuild a bow by creating a mold from sheets of melamine. Then epoxy it to the cut open hull. And this was an age old technique using little more than hand tools and common sense.
