Suits made in the American tradition sit differently on the body than their British or Italian counterparts. The distinguishing feature is what is not there.
The shoulder is where jackets diverge
A suit jacket's shoulder can be built up with padding and canvas to create a defined line, or left close to the wearer's own slope with minimal reinforcement.
The British military-derived tradition builds it up, producing a structured silhouette that holds its shape independently of the body inside it.
The American approach reduces that structure, following the natural shoulder. The jacket reads softer and moves more with the wearer.
The market wanted a garment for daily wear
American suits were sold in enormous volume as ordinary business clothing rather than as formal dress. A jacket worn from a commute through a full working day cannot be rigid.
Reducing internal structure makes the garment lighter and cooler, which mattered in a country with long, humid summers and, later, air conditioning that varied by building.
The softer construction also tolerates a wider range of body shapes off the rack. That was essential to a business built on ready-to-wear rather than bespoke.
Manufacturing reinforced the aesthetic
Less internal structure means fewer hand operations and fewer components. A jacket with a lightly padded shoulder is faster and cheaper to produce than a fully structured one.
American clothing factories were built for scale, and the design that suited scale became the design that defined the look. Aesthetics and production converged.
The straight, unsuppressed body of the classic American cut follows the same logic. Fewer shaped seams means fewer places for the fit to go wrong.
Softness is not the same as cheapness
An unstructured jacket exposes the quality of the cut, because there is no internal scaffolding disguising a poorly shaped armhole or an ill-judged balance.
Achieving a clean line with minimal padding requires a better pattern, not a lazier one. This is why unstructured tailoring is common at both ends of the price range for different reasons.
The tell is the canvas. A floating chest canvas that shapes to the wearer over time behaves differently from a fused interlining, whatever the shoulder looks like.
The style outlived the occasion
As American offices abandoned daily suits, the soft jacket survived where the structured one did not. It works as a separate over knitwear and denim in a way a rigid jacket does not.
Unstructured blazers and shirt jackets in current ranges descend directly from that construction philosophy. The lineage is in the shoulder.
What began as a way to make formal clothing wearable all day became the reason the garment stayed in the wardrobe after formality left.