Created to refer to a sorry state of affairs, which would not be worth getting out of bed for. Essentially, all people with common sense would only arise from slumber from sustenance. So when something is shit, and it's not delicious and made of bacon sandwiches, remember, fuck it. It's just not breakfast.
"Hey baby, I'm afraid your mother is on the phone, your car has been stolen, and there some bills in the post."
"Yeah, but That's just not Breakfast! IS IT?"