This is kind of a funny question. Like anyone is going to say "Um once or twice a month I guess" or "Never" even though you know that is probably true of some people.
I floss every single day, unless I am sick or something and spend the whole day in bed. Flossing keeps your gums tough and they won't bleed when you get a dentist cleaning. It clears out pockets of bacteria that cause gum disease. And of course it prevents cavities and freshens breath.