Off the top of my head, I can think of at least three recent meetings/phone calls with prospective clients during which the prospect said "we don't see the need for SEO" or "nobody is actively searching for our product, online" (side note; I also had a prospective client say to me "we only do business in Ohio and Florida. Why do we need a website, anyway?") Really? You offer a product and/or service, and nobody is looking for what you sell? Then how/why are you still in business?
Considering how many times I've heard this type of remark, I'm sure many other businesses out there have the same feeling- "Why do we need to worry about our online presence?" "Why do we need to worry about having a technically optimized site?" "Why do we need anything more than a brochure website?" And last but not least, "People only come to our site if we've told them to."
The three businesses I mentioned are a bank, an insurance broker, and a manufacturer. None of the three have an ecommerce site, and in reality, none of them need an ecommerce site. That said, however, all three offer products/services that fill a very small niche in their marketplace, and none can rely solely on their existing clientele if they hope for continued growth. They need to bring in new business, and with the small sales forces each of the three companies employs, they need to rely in part on their online presence to help drive more traffic.
While a company may not have the budget to run a monthly campaign, a site built on a proper content management system will at least allow them to technically optimize their site. Why spend a bunch of money to put together a website, if nobody is going to find you? An awesome site is great, if people know you exist. That can happen through your sales force or through word of mouth, but if your prospective client doesn't know you exist, and doesn't know that you have what they need, they'll end up going to your competition.
So, how to counter the belief that "nobody is searching for my services, online"? Well, start with a quick analysis through the Google Keyword Planner to show your prospect that, yes indeed, people out there are looking for your product or service. Then a high level review of their existing site to show them that the people who ARE looking for them may not be finding them due in part to lack of technical optimization. Any knowledgeable SEO provider can point out proper (or improper) meta title tag formatting (e.g. "Web Application Develoment Company | Search Engine Optimization Company | WRIS Web Services" as opposed to "Home") or improper ALT tags on images (e.g. "DSC_001.jpg" vs. "Motor Vehicle Accident" on the page of a personal injury attorney). When people start to see that there are clear issues with the way their site is currently built, and that people ARE searching for them (without truly knowing who they're searching for), they're that much more likely to see the need for a targeted SEO campaign.
It all goes back to our belief that a great site is only half the battle. If prospective clients don't know you're there, and can't find you, a great site may be wasting your money.