It's something of a habit in our family. We put the bread on the table in a basket, covered up, then tend to forget about it for rest of dinner. After we finish eating, someone will invariably announce that they're having their Polish Dessert: eating bread after finishing the rest of one's meal, particularly when no one at the table had any during the course of the meal. This nomenclature is handed down from my grandmother, for whom Polish was her first language even though she was born in the United States.
Now, given that the vast majority of Polish food and customs in the US came from emigrating peasants, this usage makes sense. It's always been a custom among people brought up in hard times to soak up the remaining sauces and/or gravy of the meal in pieces of bread before eating it. The fact that this is called a dessert is likely a testimony to the alleged deficiencies of the Polish people in various areas that have caused them to be the butt of a great many jokes.
Personally, I hate gravy-soaked bread. I'll take my dessert with a bit of butter, thank you.