There is one major reason why people feel the need to get all romantic on Valentine's Day. It is that big business and the media is telling them to.
The true romantics don't need to ring-fence February 14th for their loving gestures. They indulge them all year round.
For the rest of us, there's a cynical sense of being told what to feel and do, how to think and when precisely this should all occur. If we don't conform, then we'll feel the wrath of our significant other. If there's no love interest in our lives, then we're just a failure and need to get one fast for February 14th.
It's patently time for a party! In protest, of course.