Hobbits are very concerned about the idea of adventure. As Bilbo said, adventures are "Nasty disturbing uncomfortable things! Make you late for dinner!" And I can't say I much disagree! You have to be a little bit cracked to want to go on an adventure. Think about it. If you had the choice between a comfortable life where you have all the jammy muffins and frosted scones you could wish for, a warm home filled with creature comforts, a strong community--and sleeping outside on the rocky ground in the cold rain eating what sour berries you come across (and perhaps a mangy squirrel if you're lucky), risking life, limb, and happiness to accomplish some goal you think is for the greater good, which would you choose?
But somehow, something "Tookish" wakes in us, and we wish to see great mountains, hear pine trees and waterfalls, explore caves, and trade our walking sticks for swords. And more than that, we actually do it. Drawn into adventure--into risking it all--against our better judgment. So what drives us reluctant heroes to abandon elevensies in favor of hard tack?
1. It Wasn't Really All That: Humble Hobbits
When the fate of the world hangs in the balance, the hero technically has a choice--but it isn't much of one, because with the way the world's going, you're all going to die if the hero doesn't fix whatever problem drives them to action. Frodo is a hero of this kind. Where Bilbo could have sat comfortably in his hole and lived out his days without ever seeing Lonely Mountain, Frodo knows that if someone doesn't destroy the one ring, there won't be a Shire anymore. In Delirium, it's similar, only in Delirium, the metaphorical apocalypse has already happened, so protagonist Lena Haloway has the choice to return to the ruined life she had lived, or try for something better.
These heroes have one foot in the world of necessity and one foot in the world of conviction. These characters get to be idealistic, wanting to help save the world and believing they can do it, without suffering from excessive pride (believing they are chosen, and that they alone can save the world). Their lives are such that they may not have much of a choice, when the call to adventure presents itself, but there is a choice. And so they get to be both heroic and humble, in contrast to the cowardly man who would not go on the adventure and the brash man who was not called but, motivated by pride, would steal the adventure for himself.