Why are brick ovens used to make pizza?
This is partly about temperature, as brick ovens can get to the 600 degrees F that you cited...and beyond...so, yes, potentially much hotter.  It is also about heat retention.  Further, the low ceiling is a factor.  "Best" is certainly subjective because there are a variety of pizza styles, but the advantage of a brick or stone oven is in the design.  The construction allows the baking surface to heat to a high temperature and then retain that temperature as multiple pizzas are cooked.  This is critical for crust development.  The low ceiling allows the top of the pizza to be cooked quickly, preferably charring the surface crust in places, and cooking a Neapolitan style pizza in 2 - 4 minutes.  Why are they used?  Well, they were around long before deck ovens.  They are an efficient design that has stood the test of time.  They make great pizza.