In my opinion, websites do not bring much to the table to that kind of SMEs, unless they offer some added value (online booking or something). They're just the modern equivalent of a Yellow Pages listing. A creative company probably can add a lot more value though, but I don't think a website drives business unless it becomes a part of a wider marketing strategy (my experience is not in the U.S., it might be a lot different there).
You're also mixing two very different kinds of services, professional services like accountants are VERY different from someting like a beauty salon or a cleaning service.
Social media in general and Facebook in particular, on the other hand, bring a lot of value to the second category of business owners (beauty salon, cleaning service), and make engagement with customers a lot easier.
I think Yelp or equivalent listings are also important for SMEs to monitor.
In spite of a lot of effort by several startups, there still isn't a great solution for "local" services.
I might treat it primarily as a kind of internet business card (at least at first, even if I had no idea what else to do with it), but if I had a small local brick and mortar business, I absolutely would have a website. The reason I would do this is because so few SMEs do this that it means when people are looking online for local small businesses that are not a franchise of a large chain, if you have a website of any kind, you will stand out from the crowd.
It is shocking to me how little info there can be online about locally owned businesses. I live without a car and have for several years. So I use the Internet a great deal to find information before I make the long walk to check things out in person. Thus, this is something I have a lot of familiarity with: There is a dearth of good info online about local businesses that I might be inclined to go to if I had any idea they were there and what they offered.