These three characters—Jude and Sue's aunt Drusilla, the widow Mrs. Edlin, and Phillotson's friend Gillingham—are all on hand to give helpful advice. But the people they are advising—Jude, Sue, and Phillotson—never seem actually to take this advice. Let's take a look at some advice that Jude's aunt tries to bestow on him:
'The Fawleys were not made for wedlock: it never seemed to sit well upon us.' (1.11.19)
And in fact, Aunt Drusilla turns out to be right: Jude finds himself married once, to the disastrous Arabella Donn—and then married again to the same horrible woman! If Jude had listened to his aunt, perhaps everything would be different.
So why does Hardy include both Aunt Drusilla's positive advice and the horrible decisions that Jude actually makes? Why not just let Jude take Aunt Drusilla's advice? We think that the novel features these three advisors to emphasize that our main characters are all deeply stubborn people who insist on following their own paths, even if it leads to their destruction. They may know that they are about to do something stupid, but gosh darnit, that's what they've decided to do. No paltry advice from an aunt or a friend is going to change their minds.
Take, for example, Phillotson's friend Gillingham. When Phillotson is ready to give up his marriage with Sue, Gillingham yells at him:
'But if people did as you want to do, there'd be a general domestic disintegration. The family would no longer be the social unit.' (4.4.46)
Gillingham is shocked at Phillotson's decision to go forward with his divorce, since he views divorce as a threat to the family as a social unit. But Phillotson is so convinced of the rightness of giving Sue her freedom, even though it costs him his job and his social standing, that he refuses to regret his decision. We admire that Phillotson sticks to his guns, and this argument with Gillingham gives the novel an easy way to draw our attention to Phillotson's stubborn principles.