The Default Behaviour will only be active if no Behaviour matched for both foreground or background apps. The Default Behaviour is then used regardless of which app is in front, so it could be active for f.ex. Finder, Console, Terminal, System Preferences, ..

As long as you run iTunes, the iTunes Behaviour will match and prevent Default Behaviour from becoming active.

If you have actions that you want to use when Finder is active, you'd need to create a new Behaviour for Finder in the Behaviour Construction Kit - and then assign your actions to it.

This Behaviour will then be active whenever Finder is active - regardless of which other apps are running.

Best regards, 
Felix Schwarz