Backend development is important when developing a web application or website that requires a database, security, dynamic content and scalability. However, there are some instances where Backend development may not be necessary, such as in the case of a static website with only HTML, CSS and/or JavaScript, similarly Backend development may not be necessary when creating a mobile application that is just a wrapper or front-end interface to an existing API. In either case, the decision to use Backend development or not will come down to the specific needs of the product being developed.