Hey dol! Merry dol! Get lost Tom!!!

[Bêthberry]

In addition to what Son of Númenor says about wanting to preserve his own special image of Tom, I think there is another issue with the omission of The House of Bombadil and also of Fog on the Barrow Downs.

Both of those chapters provide initial scares for the hobbits. Gandalf even says, later in Rivendell ("Many Meetings") that Frodo's experience with the Barrow Wight was more harrowing than that on Weathertop. The book thus gives us a graduated development of the tension which the Black Riders cause.

The movie lacks this progression of fear and suspense and terror. Thus, the Prancing Pony and Bree in the movie must in effect become darker than those scenes in the book. And the movie has to rely on big screne action instead of finely wrought emotional development. In missing out on Old Man Willow, movie goers also have little foreshadowing for the likes of the Ents in Fangorn.