Going to a department store and buying a suit meant, back them, roughly the same as havin a suit made to measure nowadays in a retail store. Either you had a ready made model altered or you had the same model purposely made in your size and with your specifications. This explains why it the cut of vintage garments varies a lot withing the same brand: they were adapted to the client.
The thing of going in a shop, buying a suit and expect to wear it straight away is a modern thing.