The movies failed to fully deveop the Hobbits into the heroes they were to become by leaving out the raising of the Shire. Without that essential scene, the four Hobbits kicking ass and taking names, unafraid and unprotected by the great heroes of the story, they really do show that they have changed.
I'm not as convinced that the Scouring of the Shire is as essential to the growth of the Hobbits as people often assume. By the time of the Scouring of the Shire, the Hobbits have already done the developing- the Scouring of the Shire is simply an end of term exam showcasing how far they've come. This i believe is one of the critical mistakes in assessing Tolkien's use of 'personal development'- people demand these 'road to Damascus' moments where everything is spelled out in order to assess development rather than being able to pick up on the incremental change of perception and attitude which is the reality of human behavior. Realism is not obtained through the kind of 'Either get busy living or get busy dying' rhetoric and motivational platitudes beloved of the big screen and while those moments make for fantastic drama, they are dramatic precisely because they almost never happen in real life.

With the Scouring of the Shire, the major purpose of it is to show that after enduring so much, after going through the crucible of war, the very world you looked forward to returning to no longer exists. Tolkien made this apparent in a very visual, dramatic fashion, however i believe the films achieve just as evocative an effect more along the lines of Remarque's 'All Quiet on the Western Front', depicting a subtle but profound alienation to the otherwise unaffected world

Dr Death