You can thank Outback for introducing the Bloomin Onion back in the day, for the popularity of the design that allows the cooler space below the burners to catch the breading that falls off of the food, without burning it. They did not come up with the design by any means, but everyone trying their own version of the Bloomin Onion made the design very popular for a few years. Whether or not it is needed really depends on what you cook (breaded or not) and how often you filter the oil. That oil sitting down there below the burner with the breading that fell off while cooking is not really used in the cooking process and is just thrown out. If you cook french fries and filter your oil often, like places like McDonald's does, you waste money on oil by having that space below the burner. If you cook a lot of breaded stuff, and want a little more time between filtering / replacing your oil, it is a big plus.