In the early 80’s I worked at Merry-Go-Round. Our specialty was designed jeans. We definitely didn’t have any creases down the front of the leg. Later, I worked for County Seat (still in the 80’s). They sold a lot of Levis. No crease there either. In the 90’s I worked at Armani Exchange within Bloomingdale’s. No creases.
There was a time that they made trousers out of a lightweight denim. The pants had pleats and creases. That came and went.
Some dry cleaners put a crease in all pants, unless you tell them not to, and they still sometimes screw it up. This is a forever mystery to me. Why would you add a crease when none is there? The designer/manufacturer sent the pants to the store as they are intended to look and be worn. Some people dry cleaned their jeans back in the day to keep them dark, and the dry cleaner would start the whole crease thing.