Streams and observables have become crucial in modern web development due to their ability to simplify complex data management in applications. Libraries like RxJS, often used in frameworks such as Angular, facilitate the stream-based approach, which shifts the paradigm from actively requesting data to passively listening for it. This method effectively addresses common challenges in web applications, such as managing multiple independent components that need to remain in sync, handling real-time updates, and merging data from diverse sources like APIs, user inputs, and sensors. Streams build on the Observer pattern, where "observers" react to data emitted by "subjects," allowing for efficient and asynchronous data processing without constant polling. By using streams, developers can create modular data pipelines that can be easily manipulated and extended. Streams not only simplify the coding process but also enhance the overall efficiency and responsiveness of web applications.