Fins are used to move the center of pressure of the rocket aft of the center of mass, helping with stability. The issue is if your fins are too big, they can make you too stable, and you end up having difficulty with control authority. Most of those fins are in the "too big" category. As for the rocket itself, it turns out that the drag difference between a simple cylindrical body with a pointed tip and something more aerodynamically optimized is actually pretty trivial on the scale of getting to orbit, and it's a heck of a lot easier to roll some sheet metal into a tube than to make anything that complex--and assembly labor is a big driver in rocket launch costs.
In space, it's even worse. The fins rely on air pressure to induce stability--no air, no benefit. And ditto for those streamlined body shapes. No air, no problem with the most unaerodynamic shapes you can imagine. The LM is the classic example of a vehicle designed only for spaceflight, and it's about the ugliest thing you'll ever see. It's not even symmetric! The oxidizer tank of the ascent stage was heavier than the fuel tank, so the fuel tank had to be placed further off the centerline to balance the center of mass over the center of thrust, which can be seen in the shape of the "cheeks" of the LM ascent stage below. (The oxidizer was also denser, hence why the tanks are still roughly the same volume.)
EDIT: Probably worth saying that those designs were, themselves, based on rockets like the V-2, which were almost entirely atmospheric during their flight, and thus did get a fair bit of benefit out of reduced drag. The popular image of rockets then took that shape and exaggerated it for aesthetics, stretching the fins and curving the body more, while the real vehicles were doing just the opposite--eliminating fins and simplifying the body form.