Because going to the moon and coming back means going back and forth to the moon, which means a very long distance, which means a lot.
You can also say: I love you until the stars come back. Literally, I love you as if I have gone to the stars and come back, which shows that I love you very much.
Extended information Mike Sam Brenne's children's book "Guess how much I love you" (guess how much I love you), Big Nutbrown hare said to Little Nutbrown hare:
"I love you to go to the moon and come back."
Yes, I love you, from here to the moon and back.
The original text is as follows:
Now, it's time for little rabbit to go to bed, but she holds big rabbit's ear tightly. She wants to make sure that Big Nutbrown hare is listening to her.
She said, "Guess how much I love you?" Big Nutbrown hare said, "Oh, I can't guess."
Little Nutbrown hare said, "So many." She spread her arms as wide as possible.
But the big chestnut rabbit has longer arms. It says, "I love you very much." "Well, that's a lot." Little Nutbrown hare thought.
Then the rabbit had a good idea. She turned over, put her feet on the trunk and said, "I love you until the tip of my toes."
Big Nutbrown hare throws Little Nutbrown hare on his head: "I love you to your toes."
Little Nutbrown hare said, "I love you as high as I jump." She kept jumping up and down.
Big Nutbrown hare smiled and said, "I love you as high as I jump." He jumped so high that his ears touched the branches. Little Nutbrown hare thought, this is really jumping too high. I wish I could jump that high.
Little Nutbrown hare shouted, "I love you, as long as this road extends all the way to the river." Big Nutbrown hare said, "I love you all the way to the river and then over this mountain."
Little Nutbrown hare thought, that's really far away. At this time, the little rabbit saw the dark night sky, and nothing could be farther than the sky.
She said, "I love you as far as the moon." Then she closed her eyes. Big Nutbrown hare said, "Oh, that's really far, very, very far."
He put the rabbit on a bed made of leaves, bowed his head and kissed the rabbit, saying good night to her. Then, he lay down beside the little rabbit, smiled and said softly, "I love you as far as the moon, and then come back here from the moon."
Walk into your dream with warm love. May every child on the earth be surrounded by love.
I love you until the moon comes back. ..