Why/How should I used objects in JavaScript?

I understand how to instantiate objects and call them, but I just cannot find a reason to use them in my script. I could do

var obj = {
    hi: function() {
        return "Hello";
    }
}; 

but why can't I just do it the same way like:

function hi() {
    return "Hello";
}

I've never understood the reasons why I should use prototyping either. Most of the things I do in JavaScript I can do well without objects. But I want to use objects. What are objects for and what are the reasons why I should use them?