Yes, there are areas for those on the UI, but if everyone used it, why give us the icons to place on the toolbar.
Honestly I think that the problem is that unless you expand up to setting 3 of the toolbar you only have 1-8, when most games have slots for all the numbers, and the - = buttons. Add that would give us 8 more slots when using toolbar setting 2.
Personally I use toolbar setting 2 since the buttons for my BO abilities are placed at the bottom, seperate from the toolbar, but that is not how everyone does it and adding these 4 slots per toolbar row would help out alot.
While the slots are not visible, they are still there, so it would be possible to use them for something when you don't need visible feedback on the cooldown status. Just switch to setting 3, fill up the end of the first two toolbars, then switch back to setting 1/2. Not ideal perhaps, but it does work.