Why should we use Observer/Pub-Sub pattern here?

I am trying to learn Observer and publisher-subscriber pattern.

came through this simple example here

Problem: There is a button and onclick of the button it should be updating the count.

without any pattern i can do simply as

window.onload = function() {
  var container = document.querySelector('.container');
  var count = 0;
  container.querySelector('#click').addEventListener('click', function() {
    count = +document.querySelector("#count").innerHTML;
    count++;
    document.querySelector("#count").innerHTML = count;
  });
}

<div class="container">
  <input type="button" id="click" value="click">Total Counts: <span id="count">0</span>
</div>

In the above link that i have shared about observer pattern it has an implementation for the same using observer pattern jsbin

My Question here, is the usage of a pattern not complicating the code. I am really having a bad time of understanding what exactly the code is trying to solve .can some one please explain this and what is this.notify doing in the jsbin code.

Please help

Thanks