Because Lennie doesn't want to be away from his new pup.
George says Lennie wants to sleep in the barn that Friday night because Lennie likes soft things to touch and the hay in the barn is soft for him. Lennie also likes to tend the rabbits, which they plan to have on their dream farm, so being in the barn allows him to be closer to them.
George knows that Lennie will want to sleep in the barn on Friday night because Lennie always wants to tend the rabbits there, and it brings him comfort and joy. Additionally, George wants to keep Lennie away from the other ranch workers because he knows they can be mean and may potentially harm Lennie due to his disabilities.
He tells Lennie that he won't say a word when they see the boss, and he says that if Lennie gets in trouble, he should go hide in the brush where they are right now.
Lennie slept in the barn because George told him to go there and hide after an incident with Curley's wife. George knew Lennie needed to be somewhere safe until he came to get him.
George instructs Lennie to hold onto the idea of their dream farm and not to speak or interact with anyone at their new job the next day. He also reminds Lennie to stay out of trouble and avoid conflict with the other ranch workers.
In Chapter 1 of "Of Mice and Men," George instructs Lennie to remember their meeting spot by the river in case he gets into trouble. He also tells Lennie to stay quiet and not say anything when they go to the ranch the next day. George emphasizes the importance of Lennie following his lead and not causing any trouble.
George knows that Lennie's cognitive impairment would prevent him from being able to care for himself successfully. Without George's guidance and protection, Lennie would likely struggle to meet his basic needs and may unknowingly put himself in dangerous situations. George believes it is best for Lennie's safety and well-being to stay together.
George and Lennie stop at the bank of the Salinas River to rest and drink water. This allows them to escape the harsh realities of their itinerant lifestyles for a brief moment and to enjoy the peace and tranquility of nature before reaching the ranch where they will start working.
He tells Lennie that he won't say a word when they see the boss, and he says that if Lennie gets in trouble, he should go hide in the brush where they are right now.
Sleep until Friday.
To me, as I was drifting off to sleep one night, it sounds like George Clooney.
They Sleep at Night.
There could be a variety of reasons why George may not want the pup to stay. Perhaps he has allergies, does not have the resources to care for another pet, or has other personal reasons. It's important to respect George's decision in this situation.