Many people believe they can build a website and sit back and traffic will come. Unfortunately, for them, this is not going to work unless they just happen to have something so rare and extreme, there are very little competing keywords. Websites need to be optimized with proper and relative content, keywords, and Meta tags for search engines to properly find them and rank them. They also have to be submitted to the search engines and have links built which point at the website to help it be found better. All of this is possible to do yourself but takes lots of time and a decent understanding of how to do it properly.
To save yourself time and get your website found, it is generally worth the time and expense of hiring a link building service to use their knowledge and know how to get your website moving up the ranks. A link building company will look at your website and make recommendations on what you need to change to improve your visibility. Another advantage to using a link building service is they will use blog and social media services to get one-way links in place pointing at your website.