It could be useful for protecting the carpet from muddy or snowy boots, or from other fluids spilling. Just as easily a smaller size plastic tub could serve the same purpose. I keep a canvas bag with cleaning supplies/ fluids secured to the passenger side with the webbing and snap connector that originally restrained the charger cable. There is a small, deep storage section beneath the trunk floor which might require that the trunk be completely emptied in order to gain access, with a trunk tray installed. Items may also tend to slide more easily on the tray as opposed to carpet.