Stacia,
I'll explain if I may. First, the medals are a merit system. They are factored into promotions. Second, they are a source of pride… a way to display accomplishments to your fellow soldiers. Third, each branch of the military is about tradition. These medals harken back to the earliest days of the military. The Purple Heart goes all the way back to the American Revolution.
Tradition is important in the military. Like the tradition of civilian leadership over the military is ingrained. Also like the tradition of non interference in politics. This isn't the case in many other countries. Those in the military reinforces our traditions every chance we can. I for one hope awarding medals never goes away.