Why is the external style sheet useful?

[vidushi-tomar-7f335103 (Vidushi Tomar)]

Why is the external style sheet useful?

[vivek-pandey-2082921b (vivek pandey)]

When working on a large project or capstone level project internal and inline css will be very complex and will need a lot of attention where as using external css you can pay proper attention to both HTML and Css side by side and the code will be scalable and much cleaner.