People wore 50+ pounds of armor because it stopped things from killing you. When plate armor was developed, people stopped using shields because their armor could protect their whole body. The only way to hurt someone was to get between the joints or areas like slits on a visor. Hollywood depicts swords like they’re fucking lightsabres that cut through solid steel.

an addition to this:
hollywood also depicts arrows as if they punch straight through a breastplate
and also holding a 100+ lb war bow at full draw for like a minute straight without screaming and loosing the arrow wildly as your muscles give out