@ your comment m0o: Why not doing it any other day? Very simple: incentive. Not just for us, but for her parents. Dramatization: "Mom, can I go bowling with Jeffrey?"..."Well deary, you have a lot of SAT prep to do. I am not sure that spending this weekend with him is such a great idea right now." ... "But mom! It's Valentine's Day!" ... "Oh right you are! Well enjoy yourselves!".
Valentine's Day is an excuse for kids to tell their parents they want to go out instead of doing work and having somewhat of an excuse. It's also a joyous occasion to simply say "it's Valentine's Day!" and instantly create a happy, joyful, and somewhat romantic atmosphere. Just because the day itself is suppose to symbolize the feeling of love and happiness permeating through the air.