Why do Star Wars Stormtroopers wear all that armor if it doesn't have to help them in any way?
Stormtrooper armor is designed for a different purpose than conventional battle armor.During the Clone Wars the initial clone armor was designed like a conventional ballistic armor. It was tough enough to deflect shrapnel as well as slug rounds and some blaster bolts. It was by no means impregnable, and just as with modern ballistics armor high power blaster bolts could easily burn through it, and it's strength would deplete the more punishment it took. Clone armor did offer the soldier fairly reliable protection against small arms, but since it was designed by the Kaminoans with a relatively limited understanding of human biology it was cumbersome and uncomfortable to wear.Later in the Clone Wars the armor was redesigned to be more comfortable to wear as well as include features like an improved vacuum seal and filtration system. This armor still offered outright protection that allowed a soldier to keep fighting after being shot. Phase two armor was really high quality and a nice piece of kit.When the Republic transitioned to the Empire the Clone Army was kept for a few years. The first Stormtroopers were just phase two clone troopers. When the Empire started transitioning to a volunteer army the clone armor was dropped in favor of this:The Imperial Stormtroopers were issued cheaper armor that while providing protection against slugs and shrapnel did not have the clone armor's ability to outright deflect a blaster bolt. Instead the Empire opted for a design that would disperse the bolt's energy across the trooper's body. The result was that when a Stormtrooper was shot the soldier would likely be knocked unconscious or at least given a nasty blow, but the trooper would still be alive. The Empire would mop up following a battle and collect their unconscious soldiers. Most of the Stormtroopers shot in the movies would be able to return to action following the onscreen battle.