I am curious why would anyone expects that 3d printed tanks are a good idea. We have sheet metal, it has well controlled and probably close to optimal performan

I am curious why would anyone expects that 3d printed tanks are a good idea. We have sheet metal, it has well controlled and probably close to optimal performance (that is, the maximum mechanical resistance that you can get out out of a given mass of aluminum or stainless steel). The resulting rocket is a long, hollow tube. What exactly do you gain by 3d printing the entire body, other than a nice investor buzzword? I could see a gradual move to 3d printing, the engine of course with it's complex features, then the bulkheads, downcommer & manifolds, maybe fairing and other aerodynamically shaped pieces etc. But why would you try to print sheet metal transversely, one slice at a time? What possible design you could think of, other than a long, slender tube, that can utilize the flexibility of 3rd printing and provide value to justify the necessarily reduced mass ratio ?