Java is a potent imperative language. If you need a language that precisely controls what a computer will do, Java is hard to beat. Given the prowess of Java, why would you ever create a new imperative language?
One justification for new imperative languages is simplicity. You may want to offer your users a language that they can master more quickly than Java. If your users are nonprofessionals, and especially if your users are children, you will want to provide a language that is easy to learn.
Another justification for creating a new imperative language is specificity to a context. UNIX shell script languages are excellent examples. These languages include built-in knowledge of the file structure and other features of the UNIX operating system. A UNIX shell lets users quickly learn a powerful language that controls the UNIX environment.
Many other applications call for flexible but precise control, and new application-specific languages may fill a niche. If your domain requires a flexible framework for issuing explicit commands, an imperative language may be the answer.