When I find an interesting company online---maybe I'm searching for a product I need to purchase, I always take a look at the posted "About Us" page. Woe to any company that doesn't post who they are; I'll leave the site. I like to know who I'm doing business with.
What does your "About" page say about your company. This is a place to identify with your customer, seal a sale. The page should include your corporate mission statement. A bit of company history is always a plus. And a personal account of the CEO puts a personal touch on the company.
A separate "About" page is not necessary if you include these components on your home page; but identifying the who's and why's of your business is important to your online success.