3D printed objects aren't the strongest due to the way the layers are laminated together. I imagine the last place you'd want a weak join is on a 150+ foot long blade swishing through the air.
Especially since a spinning blade gets more efficient as it gets faster. Higher speed = lower torque for a given horsepower density, so a higher tip speed ratio (TSR) wastes less energy "twisting" the air downwind.
Efficient wind turbines run at a TSR of 6 or higher - which means that in windy conditions the tips are running at an appreciable fraction of the speed of sound.
If one of those puppies breaks off it's NOT the kind of baseball bat or boomerang you want coming toward you, whether flying or summersaulting along the ground. (Imagine a caber toss with giants and redwood logs.) Not to mention what the resulting unbalanced spinning does to the other blades and the pylon.