A guy walks into a bar. He orders a drink, and scans the room for cute girls. According to several evolutionary studies*, his personal ranking in the global mating scheme is inversely proportional to the number of chicks who leave the bar with someone other than him.
A guy walks into eHarmony. He creates a profile, then assiduously searches the profiles of potential mates, skipping the ugly ones, blowing past the neurotic ones, etc., and eventually mustering the courage to write a message to one or more of the cutest girls. The guy receives no perceptual feedback of rejection, either through lack of response (there are many reasons why someone might not write back — too busy, missed the message, etc.), nor the counts of females who have glossed over his profile in their own searches. His personal rank in global attractiveness therefore is merely proportional to the pool of available profiles spanning the entire Internet.
*not mentioned here out of laziness