Can someone explain why on earth a wallpaper cache is necessary for anything? Admittedly I just use whatever wallpaper comes with the current version of macOS a

Can someone explain why on earth a wallpaper cache is necessary for anything? Admittedly I just use whatever wallpaper comes with the current version of macOS and leave it for a year until the next version comes out. but even if I loved to change wallpaper two or three times a day, what would be the purpose of caching it?