Most web design companies have a hard time creating websites that demonstrate an appropriate understanding of SEO. They cut corners because it's easier to let the client dictate how a project should go rather than being a professional and making strong suggestions that will positively affect the mileage you get from your website. SEO is important during the build of contractor websites because you need to make strong suggestions for where to include more text (Google has to be able to read and understand what a page is about), and in the development process, there are all kinds of decisions being made that will affect the way Google indexes a page. Make sure you partner with a company that understands how Google reads the internet, not just a company that can make your website look pretty.