If a website doesn't have that much search volume for their primary keywords, is it worth spending money towards SEO if very few people will be searching these keywords to begin with?
SEO is much more than just keyword rankings. Good SEO focuses on the bigger aspect of web marketing which is about driving traffic from all online sources, using keywords, social media, links, content, etc. There is also the usability and conversion avenues that web marketers should be helping you improve as well.
The goal is to drive as much converting traffic to the site as possible. SEO can do that by focusing not on high-traffic keywords, but high-profit keywords. It doesn't always take a lot. But beyond that you want to make sure your site can convert the traffic it is getting. By focusing on usability issues you make a better site experience for every visitor, regardless of how they found your site.
