What is revealed by the fact that Gregor thinks the father's not reading aloud to Grete and the mother at his accustomed hour is simply "a custom that, of late, had been entirely abandoned?"

Gregor has now been cut off from humanity is emphasized by the fact that he awakens in darkness. He wakes up in his dark room and cannot hear the regular rituals that he once did. He has been isolated from everyone, a situation also brought out by the fact that his family now locks his doors from the outside and walks around on tip-toe so as to remain undetected by him.