It is very important for writers to make the effort to constantly build their vocabulary. As writers, we're in the communications business. In the communications business, a writer's paycheck grows in relationship to their vocabulary. A broad and varied vocabulary allows a writer to cover a broad and varied range of topics and ideas. This in turn provides a writer access to more potential projects.
There are many approaches to growing one's vocabulary. Some people use their reading as a way to learn new words and concepts. They challenge themselves to read magazines and books that cover information outside their normal realm of experience. As they come across words they do not know, they make a note of them and learn their definition and usage. Others pickup a vocabulary building reference book and learn a word or group of words on a weekly or daily basis. Learning another language is also a great way to learn new words, concepts and gain a new perspective when reading or writing in one's native language.
Select the approach that suits your time and your learning style. Then pursue vocabulary building with zeal. It will payoff.