PS: It was rather a tongue in cheek comment, implicating the Lispy roots of Javascript, and the increasing popularity of it among programmers.
I would bet that interest towards functional programming or Lisps will increase with such movements, and the myth might in that sense be invalid in a near future.
In the context of javascript, "unobtrusive" means it is designed to degrade peacefully in browsers where javascript is missing or disabled. In this case, the right way to attach an event handler is to assign a class or an id to the HTML element in question and add an event handler to it using an event listener in a separate javascript file, rather than jamming an `onclick="doSomething()"` attribute into the HTML element itself.
> In the context of javascript, "unobtrusive" means it is designed to degrade peacefully
Nitpicking here, but that is actually graceful degradation/progressive enhancement.
Unobtrusive JavaScript is about writing JavaScript code that plays well with others. The example you gave of not having inline JavaScript in your presentation layer (HTML) is one example. Not writing JS code in the global namespace and avoiding monkey-patching built-in objects are other examples.
Cost is one. These books would be ten times as big had they used Java examples. ;-)
Seriously now: Lisp has a very unobtrusive syntax. It seems a good fit for teaching a lot of concepts.