Why Do We Celebrate Valentines?

What is the point of Valentines Day?
I'm sure it's great for those couples that are just so in love.
But what about those who are left out?
What about those who are pushed aside and forgotten?
What about those who aren't considered pretty enough?
What happens when every one around you gets something from a special person and all you get is ignored?
Every one says that you don't have to act like a slut to get a guy to notice you.
In all of my experiences, the slut always wins.
Every one says there are more fish in the sea.
What happens if you can't find one because the one you did find likes another girl.
I just don't see why we have to celebrate a holiday that only includes a few people.