It is rude to keep someone out of a room.
Sally is playing a video game in her room when her sister knocks on the door.
Sally wants to keep playing her game.
Sally let's her sister in her room and goes back to playing her video game.
Sally locks her door and goes back to playing her video game.
Sally's sister enjoys sitting in Sally's room watching Sally play a video game.
Sally's sister is hurt that Sally won't even let her in Sally's room.