It is not mandatory to use node.js for developing angular application. You can very well go ahead without node.js for developing angular application but it would not be wise to do so. Let me explain you some of the reasons how node.js makes angular app development process easier for us:
Node allows you to spin up a lightweight web server to host your application locally in your system.
NPM (Node Package Manager) comes with node.js by default. NPM allows you to manage your dependencies. So, you don’t have to worry for operations like adding a dependency, removing some, updating your package.json.
Third and the most important, npm gives you angular cli or ng cli(angular command line interface) . Angular CLI is a great tool for scaffolding your application. So, you don’t need to write boilerplates manually.