It's not even that good an idea to use scriptlets on plain old JSPs, except in occasional small doses.
Scriptlets are logic. JSF is an implementation of MVC. In MVC, you don't put logic on the View.
Also, JSF is not a linear translation of the View definition into Java code the way JSPs are. Instead the view is compiled into a data tree. Positional logic such as JSTL and scriptlets don't fit into the tree and the results can be unpredictable. And usually bad.
Bjoke: A "Bully Joke". A Statement or action made with malicious intent - unless challenged. At which point it magically transforms into "I was just funnin'" or "What's the matter, can't take a joke?"