[Galadriel55]

Reading your post, Boromir, made me realize very strongly again that the main role of the two hobbits was to be Frodo's friends: a you could say a complicated form of emotional support. We cannot judge Gandalf's decision by the what-ifs, only by history as it happened. Could he have anticipated hobbit ambassadors to Rohan, Gondor, Fangorn, other lands? Possibly. But more immediately and explicitly he mentions friendship. Frodo is already surrounded by everything that is strictly required: strength, skill, wisdom, and representatives of every race present at the Council. The only thing he lacks is "normal people", people whom he can trust absolutely (ahem, Boromir), talk normally and unrestrainedly with (Gandalf, Aragorn), be close with (Legolas, Gimli), and who would be a piece of home on his way and a reminder of his purpose. Sam fits just about every point except arguably the last. Though he talks about home all the time, he is himself too much an atypical hobbit and too closely tied with Frodo. Pippin and Merry are less close with Frodo, and as such represent to him a view from the side of the silly ignorant hobbits that he so wants to save. At the same time, their presence is a comfort (though maybe a nuisance to the rest of the Fellowship). People to aid the unseen will battle part of the quest.