Shelob's Lair

[Manveru]

Originally Posted by Halbarad of the Dunedain

The more important and more likely reason is the timeline. The events of Shelobs Lair coincide with the Battle of the Pelennor. If they had done Shelobs lair at the time of Helms Deep, the ring would have been destroyed durring or before the Battleo f Pelennor.

if they were really following the timeline the frodo/sam storyline wouldve ended at about the spot when they reach the black gates as this coincides with the end of the battle for helm's deep and the parley with saruman