You know, it's funny....modern girls all think they're above this sort of thing....but they're not. The models in the picture may look plastic, the writing may come off as insincere or cliched, but the card is effective nevertheless.
People respond to elevated speech, to words that conjure up a romantic ideal. It doesn't matter that people don't talk that way in real life. That's precisely why we like it.
Johnny Depp (above) demonstrates how to seduce with with words alone.
For the curmudgeons out there, here's (above) some valentine vitriol.