Because it is a very class conscious society in which Pip and his family live, after Miss Havisham tells Pip to bring Joe with the papers of indenture for Pip, Mrs. Joe reacts by going into one of her "rampages" as she is so excited by the news. Then with ceremony, Joe puts on his Sunday best and Mrs. Joe accompanies him and Pip to town where she will stay with Pumblechook while Pip and Joe go to Satis House.
After Joe and Pip are brought into the room where Miss Havisham sits; when she speaks to Joe, Pip narrates,
I could hardly have imagined dear old Joe looking so unlike himself or so like some extraordinary bird, standing, as he did, speechless with his tuft of feathers ruffled, and his mouth open as if he wanted a worm. (Chapter XIII)
Then, when he does speak, Joe acts as though he were in the presence of royalty because he does not directly reply to Miss Havisham, but instead speaks through Pip, addressing him and handing him the papers of indenture to give to Miss Havisham. Even when Miss Havisham, who glances at him "as if she understood what he really was better than [Pip] thought possible," and gives Joe a bag of gold coins, he yet addresses Pip rather than Miss Havisham, thanking Pip. Once outside, all Joe can say is "Astonishing."
Of course, Pip is mortified that Joe would stand in such an abject posture and humiliate himself before Miss Havisham. Nevertheless, Joe comes down in Pip's esteem. for he now appears backward and abject whereas before, aside from his relationship with his wife, Joe was very much a man. Alone after the celebrations of Uncle Pumblechook who has wished him the "joy of money," Pip reflects,
It is a most miserable thing to feel ashamed of home.....I had believed in the forge as the glowing road to manhood and independence. Within a single year all this was changed. Now, it was all coarse and common,and I would not have had Miss Havisham and Estella see it on any account.
*In this chapter, Dickens points to the shame that the lower classes were made to feel before the rich, and Pumblechook represents the new merchant class that aspires to the level of the aristocracy and their servile attempts to be accepted. All of this is even more ridiculous as they elevate a woman who is trapped in time and space and still wears a wedding dress from her youth.