Sometimes brownies are just too soft to take out of the pan in 1 piece. Course if you're cutting them right out of the pan, it doesn't matter!
THe foil, if you bring it up over the edges of the pan, will allow you to bring up the whole batch to place it on a cooling rack in one piece.
When we made brownies at the restaurant, we used full baking sheets lined with parchment. When the brownies were done and cooled, we placed another baking sheet on top of the baked brownies, and inverted it, then did the same thing again to have 'top side up' brownies. Loads of fun flipping those huge sheet pans!