Because there is moist liquid on the lips, and the amount is very small. At first, the temperature of the popsicle was very low, which was enough to solidify a small amount of liquid on it when it touched the lips, so it stuck. This happened when I first started eating popsicles. If there is running water outside the popsicle (don't be evil, don't associate it), then its temperature is not enough to freeze the liquid on your lips. You will always find that popsicles are so smooth after eating. In addition, if you have enough patience after your lips are stuck, the temperature of your lips can liquefy and stick, and poor lips may be frozen unconscious. .