User blog comment:Dalledayul/Stupid polls!/@comment-46.129.74.31-20131114144920/@comment-17754282-20131231152751

Shelob was dropped from the Two Towers because when you line up the events of the books with the appendices at the end, those events take place during Return of the King.

As for dropped characters, well the films had a huge number to keep track of already without including the likes of Erkenbrand (who disappears from the books after Helm's Deep) Elfhelm, Guthlaf, Beregond, Bergil, Damrod, Mablung and whoever else.