You have created a great web site, it has huge potential. You have set big goal around it. Now, why to optimize that? Certainly, existing customers or those who are already familiar with your company should be able to find your site without any difficulty, but this may not be the case.
Suppose if someone has started a very good business, but he/she hasn't exposed his/her telephone number, or contact address anywhere. People won't find it. How good the business can be, no such business can exist that long.
The same thing can happen with your web site if people cannot easily locate it. Potentially valuable customers never even know you are there.
You may ask :- "I had a web site created, and the address is included in all of our advertising. Why wouldn't people be able to find it yet?"
Can you be sure that every potential customer has been reached by your advertising? What about the people who don't read the magazines or newspapers where you chose to place advertisements?