Can't adjust preload, no dampening, way heavy for what it actually does do. A fat tire at the lowest psi without risking a pinch flat would do way more way cheaper and lighter. Now this is just for bikes and ultra light weight builds. A monster engine would require a monster frame and proper wheels.
Low cost and high weight capacity are where leaf spring designs shine. Thus why every single trailer uses it, f350s have leaf spring and air suspension.
Speaking of failure waiting to happen. Check out these. Where the tubing is dimpled at the steerer tube attachment looks like a prime point of failure.