Javascript is not an essential part of web development. This tool is geared towards web pages rather than applications, where client-side scripting might play a bigger role.
Unfortunately (and with some good reason) there are still many people who use NoScript et al to browse the web without javascript.
>> Javascript is not an essential part of web development.
This is a very strong statement and I probably disagree. I am not talking about client-side applications here, but all those Google Analytics snippets, Facebook Like buttons, Discus comments etc. The script block essentially became a standard way to include third party functionality into the web page. And without it this tool is less useful than it could be.
But the html editor is a really nice one :-)