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

Why is Request validation important in Laravel applications, and what problem does it solve for developers? The key reason to understand request validation is that Laravel applications are usually composed of several layers that must work together predictably. Controllers often trigger validation directly or receive validated data from Form Request classes. 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: Controllers group related request-handling logic and commonly coordinate validation, services, models, redirects, views and API responses. The specific focus here is request validation: Controllers often trigger validation directly or receive validated data from Form Request classes. 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.