Developing an app with Flask allows for a simple and integrated approach where the main Flask file and business logic files can be kept in one project folder. This setup enables easy deployment to platforms like GitHub and Railway, with automatic updates from integrated development environments. By using Flask for the backend and tools like HTML, CSS, and Vanilla JavaScript for the frontend, the process remains straightforward compared to separating the backend and frontend in more complex setups like Next.js, which require managing multiple instances and connections.