Why does Gandalf think it is important to include Biblo as the fourteenth member of the expedition?

Gandalf believed that Bilbo was the right person to include as the fourteenth member of the expedition because he will make the perfect burglar. Hobbits are known to be light on their feet, and they can move around unnoticed. Never having been around Hobbits, Smaug will not be familiar with Bilbo's scent, and Gandalf also believes Bilbo to be both courageous and heroic.