20 Biggest Things The Harry Potter Movies Left Out
17. Winky And S.P.E.W.
In The Book
Winky the house elf is more than just an alcoholic: it is she who unwittingly allows Barty Crouch Jr to leave, she takes the brunt of the blame and her mistreatment leads to Hermione forming the Society for the Promotion of Elfish Welfare (S.P.E.W.). It gets forgotten but she also fights in the Battle Of Hogwarts.
In The Film
Everyone was already way too in love with Dobby for any other house elf to come and steal some of his thunder, so the film-makers simply chose to leave her out of the plot entirely, and not answering the question of how Barty Crouch escaped. That also meant that though Hermione was not a fan of cruelty to elves, she wasn't able to do any sort of campaigning on their behalf.
Was It A Positive Change?
Not really: the S.P.E.W. subplot would have been unnecessary, mostly, as the change in treatment of elves is better served by Harry's nice treatment of Dobby, but the removal of Winky's part in Crouch's escape and his father's involvement was a massive disappointment.
It robbed that whole dynamic of the dangers of the importance of family and the morality tale seen in the elder Crouch's assumption that his son could somehow change, foreshadowing that Death Eaters rarely change their spots.