Pip wants to be friends with Herbert because he is kind, gentle, and helpful.
When Pip first meets Herbert Pocket, he is completely baffled by the “pale young gentleman” who insists on fisticuffs in Miss Havisham’s garden. Seeing him again as a young adult, he realizes that Herbert is an excellent friend. Herbert and Pip become roommates, and Pip gets to know Herbert better.
Herbert Pocket had a frank and easy way with him that was very taking. I had never seen any one then, and I have never seen any one since, who more strongly expressed to me, in every look and tone, a natural incapacity to do anything secret and mean. (Ch. 22)
Since Pip has only recently become a gentleman, he has trouble with social conventions and basic etiquette. Herbert gently reminds him not to put his knife in his mouth or his handkerchief in his glass. Because of Herbert’s company, Pip is much less lonely and adjusts well to life in London.
Unfortunately, although Herbert is a good influence on Pip, Pip is not a good influence on Herbert. Clara, his fiancé, does not even want them to hang out together because Pip drags Herbert into debt, since Herbert won’t take money from Pip and they both borrow and spend more than they should.