I thought Valentine's Day was created by a bunch of florists and jewelers to increase sales as men bought wilted flowers and shiny rocks in hopes to barter these useless things for sex. Or at best, married men use the dying flowers and shiny rocks to either get out of trouble or to stay out of trouble. It's a good system to get people to pay for worthless things, because sex and guilt can sell anything.
And forbidden fruit is always more appealing, especially when the tastes and the outcomes of eating it are unknown. If a parent puts a cookie jar in the middle of the kitchen and instructs the children that they can eat anything they want, but they can never eat a cookie from the cookie jar of good and evil, wouldn't they always eat the cookie? Every great story has conflict though, and that one act of eating a cookie seems to have provided plenty of it.