Why is Authentication middleware important in Laravel applications, and what problem does it solve for developers?

Why is Authentication middleware important in Laravel applications, and what problem does it solve for developers? The key reason to understand authentication middleware is that Laravel applications are usually composed of several layers that must work together predictably. Authentication middleware can prevent unauthenticated users from accessing protected routes. Ignoring that boundary can lead to duplicated logic, poor security, unnecessary database work, or code that is difficult to test. Why it matters in practice: Middleware inspects or modifies HTTP requests and responses and is commonly used for authentication, authorization, rate limiting, logging and request-level policy. The specific focus here is authentication middleware: Authentication middleware can prevent unauthenticated users from accessing protected routes. This question is designed to test not only terminology, but also how the concept fits into Laravel's request, application, database, security, or deployment workflow.