To distinguish good members from bad members. For long there have been profiles of people that are just trying to hook up or using italki as an online dating website, when you come across someone with points, you realize that person is someone who actually contributes to the community and is perhaps genuinely learning a language (and not just fooling around). In the past, italki profile would display how many questions have you answered and how many of them have been choosen as best answers, and how many group discussions have you participated in, but that change some years ago with the points system. You cannot get lessons or anything from the points, they are just points.