The low probability of drawing lots for Tianjin Marathon is due to the large number of participants and limited places. Every year, a large number of runners sign up for Tianjin Marathon, but the actual number of places available for allocation is limited. So everyone's chances of being selected are relatively small. This means that the probability of winning the qualification by drawing lots is low. Although the organizers will try their best to draw lots fairly, the chances of success are relatively small due to the large number of participants.