Sometimes the BF is my only meal for the rest of the day, except for some light snacks. So I'm taking my time at breakfast and tip accordingly ($3 - $4) on the tab. But if they can't produce a zero tab, I leave only two $ bills, because I'm not a dollar tree.

On the other hand: in the European Hiltons I visit (not the HGIs) the BF is twice as good and nobody ever needs to leave a tip and still the table shines and coffee is being served as well. So in my eyes it's just an idiot thing.