Reblogging again because I need to make an addition:
It's Gandalf who advocates for Pippin (and Merry) to join the party.
'But that will leave no place for us!' cried Pippin in dismay. 'We don't want to be left behind. We want to go with Frodo.'
'That is because you do not understand and cannot imagine what lies ahead,' said Elrond.
'Neither does Frodo,' said Gandalf, unexpectedly supporting Pippin. 'Nor do any of us see clearly. It is true that if these hobbits understood the danger, they would not dare to go. But they would still wish to go, or wish they dared, and be shamed and unhappy. I think, Elrond, that in this matter it would be well to trust rather to their friendship than to great wisdom. Even if you chose for us an Elf-lord, such as Glorfindel, he could not storm the Dark Tower, nor open the road to the Fire by the power that is in him.'
Elrond: Lol no, you don't have the prerequisites
Gandalf: Dude literally no one does
Also, earlier in the same chapter:
(Pippin talking to the other hobbits): 'I shall go, unless they chain me up. There must be someone with intelligence in the party.'
'Then you certainly will not be chosen, Peregrine Took!' said Gandalf, looking in through the window, which was near the ground.
Pippin is ready to throw hands with god, but he is fully aware that he'll only get away with it because he and god are already on a talk-shit basis
'Hurray!' cried Pippin, springing up. 'Here is our noble cousin! Make way for Frodo, Lord of the Ring!'
'Hush,' said Gandalf from the shadows at the back of the porch. 'Evil things do not come into this valley; but all the same we should not name them. The Lord of the Ring is not Frodo, but the master of the Dark Tower of Morder, whose power is again stretching out over the world. We are sitting in a fortress. Outside it is getting dark.'
'Gandalf has been saying many cheerful things like that,' said Pippin. 'He thinks I need keeping in order.'
Gandalf knows Pippin is Like This, and he still advocates for him to come along.