Even if you think that your business is doing just fine without a website, you should still have one.
Think about it like this, a website is "open" 24 hours a day, 7 days a week, 365 days a year. It can help to serve people information, even while your business is not open to the public. If you do not have a website, you could be losing out on a great deal of potential business!
Websites give out information about your products and services so, even if you don't currently have one, you are probably missing out on potential sales.
For example, I had been speaking with one of our web clients for years regarding a website (before he actually decided to follow through with getting one). Every time I bumped in to him, he was absolutely convinced that he did not need a website and would never even want one. He couldn't quite understand how a website would help his local business of many years - or what we could do for him. He is a very hardworking man - and, a little old school regarding technology. He insisted that his business was running 'just fine' without having anything but local newspaper advertising.
After talking with this gentleman (on and off) over a period of a couple years, his business started lagging due to the 2008 recession. We (me and this gentleman) had a mutual acquaintance - someone that Hunter Creative Group had already created a website for. So, from this mutual acquaintance, the man finally decided to give us a shot. He ended up with a small website that was search engine optimized.
About a month after creating his new website, he confessed that he had received several sales from out-of-towners, specifically because of the website. He had been making it a point to ask any new customers where they had found out about him. He was completely amazed!
Now, he has cut down on the cost of expensive newspaper advertising and is very thankful for his custom website. He has estimated that (as of today) it has literally saved him several thousands of dollars on advertising.
So, the real answer is ... If you do not have a website, your business is at a huge disadvantage.