In a world where the Internet drives so much of business, it is incredibly helpful for small businesses to have, at the very least, a website where customers can find contact information and important details like street address, hours of operation, phone number or (for more advanced businesses) even an online marketplace. 

For me, when a company has a clean, neat, up-to-date and easy-to-find website, it gives them a level of credibility.  I am much more likely to visit a company's brick-and-mortar store if they've taken the time to market themselves online. 

A website also gives small businesses greater exposure so that they can expand their customer base.  People from different towns or states can search for local businesses and find them.  And if they use a short, eye-catching domain name, they can potentially attract customer interest from publications and promotion.  The customer will remember the name and hopefully look them up online.