A person would be able to redo and reproduce an origami by unfolding it first. Knowing how cars work requires understanding each major and minor mechanical part and their purposes.
The complex nature of the human anatomy requires people to understand each and every part of the body. How? By dissecting it. Reverse engineering is a way for us to understand how things were designed, why is it in its state, when it triggers, how it works, and what its purpose is. In effect, the information is used to redesign and improve for better performance and cost. It can even help fix defects.
Imagine if the Trojan Horse was thoroughly inspected and torn down before it was allowed to enter the gates of a city. This would probably cause a few dead soldiers outside the gate fighting for the city. The next time the city is sent another Trojan Horse, archers would know where to point their arrows. And no dead soldiers this time.
The same is true for malware analysis—by knowing the behaviors of a certain malware through reverse engineering, the analyst can recommend various safeguards for the network. Think of it as the Trojan Horse being the malware, the analyst being the soldier who initially inspected the horse, and the city being the network of computers.
