What's the purpose of segregating a virus from the blood and growing it in the lab?
2019-NCoV was first cultured by a Chinese group, as published here on January 24. China has not shared samples, but did share sequencing data in the linked paper and via GISAID. The Australian group at the Doherty Institute hasn't published yet, but did put out a press release today (January 29), and appears to be the first group outside of China to have cultured 2019-NCoV. 

Viral isolation, and in particular, culture, is an important, and often difficult step in characterizing a novel virus. Once characterized, viral culture serves as a gold standard for diagnosis. Generally speaking, the ability to grow virus in cell culture allows for a broad range of pre-clinical studies that can lead to clinical advances including prevention, diagnosis, and treatment. Consider how difficult it may be to study a pathogen if you are not able to manipulate it in a living culture. You can read about this in Murray Medical Microbiology, Ch 50. This article, which does not require a subscription, may also be of interest. The article describes a variety of historical and modern methods, but also includes some discussion about the use of viral culture.