This is a kind of open-ended question, but I'll try!
If you've used Swing, you can show them the ease and comparatively shorter code to implement similar apps. Plus, JavaFX gives you the graphical/animation/2D stuff as well.
For example, the following example Launch Order Your Pizza uses Swing-based components from JavaFX. It also uses graphics to enhance the application. I haven't tried to implement it in Java/Swing, but I know it would be longer, even removing the cool graphical elements.
If you already do Java, you have the full Java API.
NetBeans provides a lot of help for learning. There is an Eclipse plug in too.
It runs on the JVM.
And our book shows you how to write cool JavaFX apps
Just a cross-over note from another topic. Requiring Netbeans and/or Eclipse is a non-starter. I'm not switching IDEs just to check out new technology.
And I realize that it's not "required", but voiced as it is shuts out a lot of people who would rather hit themselves in the middle of the forehead with a ball-peen hammer than adopt Netbeans or Eclipse.
I'd also like to point out that as far as I know, the eclipse plugin doesn't really support JavaFX 1.2 and isn't the plugin something Sun created? Ironic? Correct me if I am wrong please, but I had all sorts of issues with the Eclipse plugin.