What Bilbo did for us was his duty to help us take treasure from the dragon.  After all, we could not fight through to the dragon but instead wanted to make sure that some of the treasure be restored to us.  We could not risk anyone but him.

Wasn’t this what Gandalf intended? Dragons do not know the smell of hobbits so he would be the best to complete our task.

I would not risk anyone else to go down those tunnels to the wretched worm.

I have done too much and risked too much to be deemed a fool.