Wartime clothing
You don't think it has to do with saving material in wartime? In the US, prior to WWII, most men's suits were 3-piece (with vest), pleated trousers with cuffs and fairly generously cut. Once the war started, there were no more vests (they went out of fashion until the late 60's), trousers were plain, no pleats or cuffs, and suits were cut narrower. After the war, the fashion in men's suits was those horrible looking hugely cut suits, mostly double-breasted, that you see in old pictures or newsreels.