Why do we send cards on Valentines's day?

people send valentines day cards because its actually nice to send to send them, and it tells the person you care about them

To celebrate St. Valentine. Of course, like many St. days, the act of giving cards only originated when people decided to market the idea in much the same way the did Christmas. People send the cards because it's another way to spend your money (this is actually a good thing, as more money in the system means that the system works better)

People send valentines cards for a number of reasons: because their 2nd grade teacher is forcing them to, because they like/love someone, because they want to make someone feel better about themselves, and/or they are friends/family who like to do things like that...