Reason suggests that if a person has a fulfilling love life, then they're less likely to to crave chocolate for the resultant dopamine rush. So if a person has love, then why should they need chocolate during Valentine's Day?
I wonder if people buying the chocolate are either: 1) buying it for themselves as a substitute for the rush that feelings of love produce; or 2) Men buying it for a Woman, hoping that she will associate the delectability of the chocolate with him. .....?
Then again, maybe it just plain tastes good.