When talking about usability, most people will refer to “simple things” like making sure your phone number is in the top right corner of your web pages so the visitor can easily convert for you.
Stuff like that is important (the point of driving people to a web site is to grow your business). However, that’s only one reason to focus on usability.
The goal should always be to improve the user experience.
The more that we, as web designers focus on the user, the better quality service we’ll provide our clients.