The decision to specialize in delivering a specific type of software development service may rule out the majority of the market you can sell to, but it also provides the advantage of significantly increased capability of closing sales with the people you are specializing in selling to; in some situations, you are also able to command a higher rate. This isn't because people have a preference for you to only develop the type of software they want, but the fact that you specialize in the type of software development they need gives them more confidence that you understand their requirements.

Additionally, because you specialize, you are able to create your marketing material and sales pitch to be more specific; to communicate exactly how buyers benefit from buying into you; whether it be your case studies, describing examples or the style of writing that appeals to the people you are marketing to, your specialism allows you to appear to be perceived...