Because it solves the cognitive load problem. Should I eat my usual ham sandwich for breakfast but now these paleo diet gurus say bread is a no-no and should now probably eat eggs with broccoli which would make my mother think I am one of those health freaks now and yada yada yada... 1000 considerations, colliding thoughts. IF's answer is "well, how about eating NOTHING for breakfast?" and this is incredibly easier. Eating nothing does not feel like breaking a family or ethnic tradition, does not feel like doing weird things, does not feel like becoming another fad buffoon who eats granola or what else is the latest fad instead of honest old bacon and eggs, does not feel like your life is being ran by Men's Health or Cosmopolitan, does not require shopping in weird shops or reading labels on things. It feels very much like doing nothing. And doing nothing is easy.

Not doing something, and just putting up with pain is far easier than doing something. For example, when lying on a couch, it is easier to just put up with an uncomfortable position than to summon the strength to move.