While need might be a strong word, by not having a web site, you are certainly alienating or not even getting a chance with some buyers in your market.
Each situation and business is different, however if you are in an area that you have a good number of business travelers, you may be able to pick up some people that would otherwise not be able to find you. If you live in an area with new developments, these will have people that may not find you otherwise.
If you do any other advertising, mailers, papers etc, a web site can help to “close the deal” by giving people more information about you.
Last, with many small businesses, you may not need more than a page or two, and having a coupon for people to print is not a bad idea.