Why is it nesscary to the story that Gandolf leave the experdition The Hobbit?

Answer 1

He had other pressing matters. You find out later that he drove the Necromancer (Sauron) out of the Mirkwood area.

Addendum:

The above is definitely the reason given in The Hobbit: Gandalf and the White Council drive Sauron from Dol Guldur forcing him to relocate to his old realm of Mordor. It turns out Sauron was ready for this and didn't suffer much from the displacement. However, it should be noted there's also a literary reason for this. In terms of plot and Bilbo's development as a heroic character, it really is required that Gandalf be moved offstage. Gandalf is too powerful, too capable, and too overwhelming a figure. If Gandalf's there, he'd wave his staff, say a few words, and all problems would be resolved and we'd have a book without drama. Gandalf can handle a few Spiders and would just talk to the Elf King who he's probably on a first name basis with. Because Gandalf is gone, Bilbo is forced to assume the mantle of leadership and save the dwarves from the spiders, then the elves, and then confront the dragon alone. This is pretty common in literature and movies. The hero must be left to face adversity alone because its through this process that he or she becomes the hero.

Answer 2

It is revealed that the wizard leaves the dwarves and the hobbit in order to attend the White Council or Council of the Wise in southern Mirkwood. They are there to drive whom they call the Necromancer (later revealed in Lord of the Rings to be Sauron) from the forest, and he settles in Mordor.

Answer 3

Gandalf leaves the Quest of Erebor twice - once merely to scout the path and know what was ahead; the other time, to participate in the meeting of the White Council and attack Dol Guldur, stronghold of the Necromancer (Sauron in disguise).

Answer 4

Gandalf left Bilbo and the Dwarves several times because he had to discuss with the White Council (Saruman, Radagast, Galadriel and others) the attack to Dol Guldur. You can find something about that in LotR appendix and in the Unfinished Tales (Third Age).

By the way, it is told that The Hobbit 2 could feature the whole White Council and Dol Guldur story, if LotR actors will reprise their roles. Christopher Lee (Saruman), as an instance, would like to reprise his role, if he will shot his part in London. Other LotR actors have been asked to or have said that they would like to reprise their roles in The Hobbit.

Answer 5

In the Hobbit, Gandalf the Grey had to leave to attend a counsel with Saruman the White and others of the Wise to decide what to do about the Necromancer of southern Mirkwood. Ultimately he participated in the battle that caused the Necromancer to leave Mirkwood.

In the Fellowship of the Ring, Gandalf the Grey fell from the bridge in Moria while battling the Balrog.

Answer 6

He had other business to attend to. The most important was to assist in forcing the Necromancer out of Mirkwood. This is a foreshadowing of the events in The Lord of the Rings. It also provides an opportunity for Bilbo to grow.

Answer 7

It was so the story could be more focused on Bilbo, and the unlikeliest one was the hero. And also to slightly set up Sauron in another form (aka. Necromancer)

Answer 8

Gandalf left so he could go to the white counsel, get the other wizards, and drive Sauron out of his hiding place.