The way you structure your code is a key factor when you define your source code organization. It will make your life easier or miserable, and once this structure is established it will become a really tedious task to redefine it. That’s why you know about the different patterns available and choose the one fits your project best.
But, why should I care about modules? Well, is the way Javascript offers to organize and encapsulate your code, and if you don’t think you need to do it, because maybe it’s a small project or you don’t care at all, trust me, you are making a huge mistake!