TLC: Why is a more polar eluent more effective at displacing the points?
Most likely you are using "normal phase" TLC plates. The stationary phase is silica gel, which has free hydroxyl groups making it a polar surface. In TLC, there is a competition for the plate between the analytes and the eluent. As you make the eluent more polar, the eluent will interact more with the plate leaving the analytes to be carried with the mobile phase.