I think appearance is a reason enough to floss daily. It's nasty when people open up their mouth and you see food hanging out between their teeth.
i'll floss if i spot food. but i usually don't..well..didn't. now i've been trying to floss everytime i brush. or at least in the morning!
so do i! i guess the nasty food i eat combined with my poor flossing and not brushing twice a day all adds up...