In the meditation practices of the Great Snow Mountain, maintaining lucidity in dreams was an extremely important aspect because the teachings believed that dreams were nothing more than the neural connections made during the body's dormant state, reflecting an unconstrained reaction to the real world. It's just that without the limitations of the physical world on the body, dreams could sometimes seem absurd and unrestrained.
Without the influence of gravity, even apples would fly, and in people's dreams, the rules of the universe are not unbreakable, hence phenomena that defy these rules may occur.
But one cannot do as one pleases in dreams, as they are still subtly ruled by human nature. Conscientious people typically have logical dreams because their neurons, due to inertia, maintain certain habitual responses of their physical self.
This is the origin of the saying "Whatever preoccupies the mind during the day carries through into dreams at night."