Because there are superpowered beings(superheroes, supervillains, werewolves, vampires, wizards, etc.) with the means to easily do that in several that I can think of. Plus there are a few characters that are into weightlifting workouts or are firefighters that likely wouldn't have much of an issue depending on the person they are lifting. And then there are those whose canon has shown them easily lifting someone unconscious even though they probably wouldn't be able to in the real world.