The story from being a book about "walking".

They show up in the hobbit and Lots simply to save a character from having to walk over swaths of "boring" middle earth.

They don't like danger, hence they won't take them to Mordor, or to Laketown in the hobbit (anti-aircraft arrows again)....

Tolkien was a hyper realist, the distances in the book were important for the story, but at times cumbersome to its developments.

In the movie, Jackson could have cared less about distances...you'd think Mordor was about as far away from the Minas Tirith as Les is from Res....which wasn't the case.