This effect can be observed in the real world, too. For example, ever been to a new restaurant which is almost completely empty? I feel more inclined to go insi

This effect can be observed in the real world, too. For example, ever been to a new restaurant which is almost completely empty? I feel more inclined to go inside if it already has a good amount of patrons if I've never been there before. Or a waiting line outside a club or even an ice-cream truck. More people in line == the illusion of it appearing to be good/interesting/crowd-approved (to an outside observer).