Why won't Pip tell the truth about what happened at Satis House?

Pip is forced to talk about his day to Mrs. Joe and Mr. Pumblechook. Pip lies in a fantastical matter, making up stories about dogs being fed veal and Miss Havisham lounging on a velvet couch. He lies, partly in spite, but also because he is sure that the two would not understand the situation at the Satis House even if he described it in detail.