Not only does a footprint protect your tent, adding years to its durability, it also converts an outside storage area to a proper living area, by providing a clean and waterproof floor. With this, your porch just turned into a living room.
Another underrated feature of a footprint is directing the moist from the ground to go around your flysheet. This removes 90% of condensation from the inside of your sleeping cabin, leaving you with a dry and comfortable indoor climate, no matter the conditions outside.