Do you have an S.O.? While you may have one who is anti-V-day (which is fine), but I'd imagine that even the one who "doesn't really care much" would probably be a little disappointed if you made NO effort to do something just a little special.
Of course, you should be nice every day, too. I think that's pretty understood.
Are you only supposed to care about your S.O. one day a year? Shouldn't you be nice every day?