Some of your competitors probably already have websites. If they do, it's likely that when that directory pops up on a potential customer's screen, they will see a listing of you and all your competitors. However, your competitor's entry will have a little icon next to it. For them, it's like having a full page ad in the Yellow Pages. Without a website, you are just one of perhaps hundreds of entries that look just like the single lines in the Yellow Pages.
Word of mouth is the best advertising there is.
No question about it. So advertising isn't really the issue for you. Having a website, especially one with an easy to remember name, will help your customers find you when they need you. Of course, your address and phone number will be there. That helps them keep in contact with you.