why do the pockets hate pip?

The Pockets see Pip as benefitting from financial support and note the change in him under Miss Havisham's watchful eye. In Chapter 19 Pip visit's Miss Havisham before he leaves for London. She uses his visit to taunt Sarah Pocket, implying Pip's advancement is of her making. This of course makes Sarah Pocket jealous as she has tried to wheedle money from Miss Havisham, or at least confirmation of inheritance, without success.