Your business needs a website.
Potential clients expect your business to have a website.
The internet is the first place potential clients go to find information. If your business does not have a website, you are at risk of never being found. A website address is also often easier to remember than a telephone number or physical address, so having a website gives potential clients the easiest way possible to find your business.
A website is always available (even when you are not).
Websites are available 24 hours a day, 7 days a week, 365 days a year (366, if you want to count leap years).
Engage your target market.
Does your business cater to small businesses, or a niche market? A well-designed website allows you to better target the type of clients you want to work with.