And where's the "much cleaner code" at the end of the article? :)

Many functions inside other function, weird "setX" functions instead of modern setters, single "useEffect(() => do everything here)" instead of clear steps in class components...

Why would I ever want to switch to this functional format? What does this give the developer?

Classes were introduced in ES6 just to get rid of that awful syntax with functions, but React devs popose to make a step back in ES5 era... Weird decision.