Well I think that a beginner should try to do this by hand at first. Not necessarily in a production application, but to learn how it works.

The difference between Web development and desktop development is the HTTP protocol which is responsible for security issues and other behaviors (sessions, cookies) that you need to understand if you want to build solid applications.

Just the difference between client and server side validation is often not understood by beginners, which is a big problem.

If somebody rely on the framework to do all the job, he's going to have security issues in his applications and other weird behaviors (double submit when refreshing a page, etc.)