Pip needs people who will tell him the truth. It is not the case that he will always listen, but we all need these people in our lives, those who help us see the reality of our lives when we get in over our heads, or just flat out refuse to see the truth.
Take a look at this instance when Biddy gives the truth to Pip:
"'Biddy,' said I after binding her to secrecy, "I want to be a gentleman.
'Oh, I wouldn't, if I was you!' she returned. 'I don't think it would answer.
'Was I absurd?' said Biddy, quietly raising her eyebrows; 'I am sorry for that; I don't mean to be. I only want you to do well, and to be comfortable.'
This piece which occurs in chapter 17 demonstrates Pip's need to reveal one of his inmost secrets to a true friend. Biddy hears it, tells him her true thoughts, and later demonstrates her continued capacity as a true friend because after offending him with the truth, she confesses her offense and then utters her intentions: to see him succeed and have happiness. These are great gifts a friend would want for another. She used this scenario to reveal a truth to Pip, but he would not have it. Although he does not embrace her ideas, at least he was able to express himself, experience conflict, and endure reconciliation. We all need human relationship which feature such gifts.
Herbert offers truth too, but in addition to the qualities of Biddy, Herbert can offer insight about what Pip hopes his expectations are. Herbert's connection to Miss Havisham and to Pip's tutor, Matthew Pocket only encourages Pip's expectation that he is being set aside for Estella
In the beginning of chapter 22, Herbert and Pip are able to laugh together over their previous meeting at Miss Havisham's house. Sometimes having established history, no matter how brutal, brings about an opportunity for a friendship to develop. Pip sees the advantage of Herbert and enjoys Herbert's company. Herbert serves as a sort of best friend who Pip reveal's his secrets to regarding Estella.